JP2024175442A - Monomer, polymer, chemically amplified negative resist composition and pattern forming method - Google Patents

Abstract

To provide a chemically amplified negative resist composition that exhibits an enhanced resolution during pattern formation and forms a resist pattern with improved LER, resolution, pattern fidelity, and dose margin, and a resist pattern forming method.SOLUTION: A chemically amplified negative resist composition comprises a monomer represented by the formula (A1), a polymer comprising repeat units derived from the monomer, and a base polymer comprising the polymer (in the formula, a is an integer from 0 to 4, RA represents a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group, LA is -O- or -NH-, LB is a single bond, an ether bond, an ester bond, or an amide bond, W1 represents a hydrogen atom, an aliphatic hydrocarbon group with 1 to 10 carbon atoms, an aliphatic hydrocarbon carbonyl group with 2 to 10 carbon atoms, or an aryl group with 6 to 15 carbon atoms, and the aryl group may have a substituent).SELECTED DRAWING: None

Description

The present invention relates to a monomer, a polymer, a chemically amplified negative resist composition, and a pattern formation method.

In recent years, pattern rules have become increasingly finer as LSIs become more highly integrated and faster. Chemically amplified resist compositions using acids as catalysts are used exclusively for processing patterns of 0.2 μm or less. High-energy rays such as ultraviolet rays, far ultraviolet rays, and electron beams (EB) are used as exposure sources. In particular, EB lithography, which is used as an ultrafine processing technology, has become indispensable as a processing method for photomask blanks when producing photomasks for semiconductor manufacturing.

Polymers with a large amount of aromatic skeletons with acidic side chains, such as polyhydroxystyrene, are useful as materials for resist compositions for KrF lithography using KrF excimer lasers, but have not been used as materials for resist compositions for ArF lithography using ArF excimer lasers because they exhibit high absorption for light with wavelengths of around 200 nm. However, they are important materials for resist compositions for EB lithography, which is a powerful technique for forming patterns smaller than the processing limit of ArF excimer lasers, and resist compositions for extreme ultraviolet (EUV) lithography, because they provide high etching resistance.

Resist compositions used in photolithography include positive types that form a pattern by dissolving exposed areas, and negative types that form a pattern by leaving exposed areas. The type that is easier to use is selected depending on the type of resist pattern required. Chemically amplified negative resist compositions usually contain a polymer that dissolves in an aqueous alkaline developer, an acid generator that decomposes with exposure light to generate acid, and a crosslinking agent that uses acid as a catalyst to form crosslinks between the polymers to make them insoluble in the developer (in some cases, the polymer and the crosslinking agent are integrated), and also usually contain a quencher to control the diffusion of acid generated by exposure.

Examples of alkali-soluble units constituting the polymer that dissolves in the aqueous alkaline developer include units derived from phenols. In the past, many negative resist compositions of this type have been developed, particularly for exposure with KrF excimer laser light. However, these have not been used for ArF excimer laser light because the units derived from phenols do not transmit light when the exposure light has a wavelength of 150 to 220 nm. However, in recent years, they have once again attracted attention as negative resist compositions for short-wavelength exposure light such as EB and EUV, which are exposure methods for obtaining finer patterns, and for example, Patent Documents 1, 2, and 3 have been reported.

In addition to the above, many materials have been developed for use in chemically amplified negative resist compositions. For example, crosslinking agents such as those described in Patent Documents 4 and 5 are used to insolubilize the alkali-soluble polymer that provides the negative mechanism used in the resist composition by the action of the acid generated when the polymer is irradiated with high-energy radiation, and many crosslinking agents have been developed. On the other hand, many attempts have been made to impart the function of this crosslinking agent to a polymer, and methods such as introducing a styrene unit substituted with an alkoxymethoxy group (Patent Document 6), introducing a repeating unit having an alkoxymethylamino group (Patent Document 7), introducing a repeating unit having an epoxy group (Patent Document 8), introducing a styrene-based repeating unit having an acid-leaving group (Patent Document 9), introducing an adamantyl-based repeating unit having an acid-leaving hydroxyl group (Patent Document 10), and introducing an aliphatic hydrocarbon group and an alicyclic hydrocarbon-based repeating unit having an acid-leaving hydroxyl group (Patent Documents 9 to 15) have been proposed.

Although some degree of performance improvement has been confirmed by these methods, satisfactory results have yet to be obtained. In order to meet the demand for further miniaturization, it is important to develop high-contrast chemically amplified negative resist materials with excellent sensitivity and limiting resolution.

Patent No. 4396849 Patent No. 4478589 Patent No. 4678383 Patent No. 4955732 Patent No. 4801190 Japanese Patent Application Publication No. 5-232702 Japanese Patent Application Publication No. 8-202037 Patent No. 3914363 JP 2003-337414 A Patent No. 4648526 U.S. Pat. No. 7,300,739 U.S. Pat. No. 7,393,624 U.S. Pat. No. 7,563,558 JP 2013-164588 A JP 2019-203103 A

The present invention has been made in consideration of the above circumstances, and aims to provide a chemically amplified negative resist composition and a method for forming a resist pattern that can improve the resolution during pattern formation and can obtain a resist pattern with improved LER, pattern fidelity, and dose margin.

As a result of extensive research into achieving the above object, the inventors discovered that when a polymer containing a repeating unit derived from a monomer having a specific dehydrating functional group is introduced into a chemically amplified negative resist composition, a pattern exhibiting good resolution and pattern shape and improved LER, pattern fidelity, and dose margin can be obtained, leading to the creation of the present invention.

（式中、ａは、０～４の整数である。
Ｒ^Aは、水素原子、フッ素原子、メチル基又はトリフルオロメチル基である。
Ｌ^Aは、－О－又は－ＮＨ－である。
Ｌ^Bは、単結合、エーテル結合、エステル結合又はアミド結合である。
Ｘ^Lは、単結合、又はヘテロ原子を含んでいてもよい炭素数１～４０のヒドロカルビレン基である。
Ｒ¹は、ハロゲン原子、又はヘテロ原子を含んでいてもよい炭素数１～２０のヒドロカルビル基である。
Ｒ²及びＲ³は、それぞれ独立に、水素原子、炭素数１～１５の飽和ヒドロカルビル基又は炭素数６～１５のアリール基であり、該ヒドロカルビル基は、ヒドロキシ基又は炭素数１～６の飽和ヒドロカルビルオキシ基で置換されていてもよく、該アリール基は、置換基を有していてもよい。ただし、Ｒ²及びＲ³は、同時に水素原子になることはない。また、Ｒ²及びＲ³は、互いに結合してこれらが結合する炭素原子と共に環を形成してもよく、該環の－ＣＨ₂－の一部が、－Ｏ－又は－Ｓ－で置換されていてもよい。
Ｗ¹は、水素原子、炭素数１～１０の脂肪族ヒドロカルビル基、炭素数２～１０の脂肪族ヒドロカルビルカルボニル基又は炭素数６～１５のアリール基であり、該アリール基は、置換基を有していてもよい。）
２．下記式（Ａ１－１）で表される１のモノマー。

（式中、ａ、Ｒ^A、Ｌ^A、Ｒ¹、Ｒ²、Ｒ³及びＷ¹は、前記と同じ。）
３．下記式（Ａ１－２）で表される２のモノマー。

（式中、ａ、Ｒ^A、Ｌ^A、Ｒ¹、Ｒ²及びＲ³は、前記と同じ。）
４．１～３のいずれかのモノマーに由来する繰り返し単位を含むポリマー。
５．更に、下記式（Ａ２）で表される繰り返し単位を含む４のポリマー。

（式中、ｂ１は、０又は１である。ｂ２は、０～２の整数である。ｂ３は、０≦ｂ３≦５＋２(ｂ２)－ｂ４を満たす整数である。ｂ４は、１～３の整数である。
Ｒ^Aは、水素原子、フッ素原子、メチル基又はトリフルオロメチル基である。
Ｒ¹¹は、ハロゲン原子、ハロゲン原子で置換されていてもよい炭素数１～６の飽和ヒドロカルビル基、ハロゲン原子で置換されていてもよい炭素数１～６の飽和ヒドロカルビルオキシ基又はハロゲン原子で置換されていてもよい炭素数２～８の飽和ヒドロカルビルカルボニルオキシ基である。
Ａ¹は、単結合又は炭素数１～１０の飽和ヒドロカルビレン基であり、該飽和ヒドロカルビレン基の－ＣＨ₂－の一部が－Ｏ－で置換されていてもよい。）
６．更に、下記式（Ａ３）で表される繰り返し単位、下記式（Ａ４）で表される繰り返し単位及び下記式（Ａ５）で表される繰り返し単位から選ばれる少なくとも１種を含む４又は５のポリマー。

（式中、ｃ及びｄは、それぞれ独立に、０～４の整数である。ｅ１は、０又は１である。ｅ２は、０～２の整数である。ｅ３は、０～５の整数である。
Ｒ^Aは、水素原子、フッ素原子、メチル基又はトリフルオロメチル基である。
Ｒ²¹及びＲ²²は、それぞれ独立に、ヒドロキシ基、ハロゲン原子、ハロゲン原子で置換されていてもよい炭素数１～８の飽和ヒドロカルビル基、ハロゲン原子で置換されていてもよい炭素数１～８の飽和ヒドロカルビルオキシ基又はハロゲン原子で置換されていてもよい炭素数２～８の飽和ヒドロカルビルカルボニルオキシ基である。
Ｒ²³は、炭素数１～２０の飽和ヒドロカルビル基、炭素数１～２０の飽和ヒドロカルビルオキシ基、炭素数２～２０の飽和ヒドロカルビルカルボニルオキシ基、炭素数２～２０の飽和ヒドロカルビルオキシヒドロカルビル基、炭素数２～２０の飽和ヒドロカルビルチオヒドロカルビル基、ハロゲン原子、ニトロ基、シアノ基、炭素数１～２０の飽和ヒドロカルビルスルフィニル基又は炭素数１～２０の飽和ヒドロカルビルスルホニル基である。
Ａ²は、単結合又は炭素数１～１０の飽和ヒドロカルビレン基であり、該飽和ヒドロカルビレン基の－ＣＨ₂－の一部が－Ｏ－で置換されていてもよい。）
７．更に、下記式（Ａ６）～（Ａ１３）で表される繰り返し単位から選ばれる少なくとも１種を含む４～６のいずれかのポリマー。

（式中、Ｒ^Bは、それぞれ独立に、水素原子又はメチル基である。
Ｘ¹は、それぞれ独立に、単結合、炭素数１～６の脂肪族ヒドロカルビレン基、フェニレン基、ナフチレン基若しくはこれらを組み合わせて得られる炭素数７～１８の基、－Ｏ－Ｘ¹¹－、－Ｃ(＝Ｏ)－Ｏ－Ｘ¹¹－又は－Ｃ(＝Ｏ)－ＮＨ－Ｘ¹¹－であり、Ｘ¹¹は、炭素数１～６の脂肪族ヒドロカルビレン基、フェニレン基、ナフチレン基又はこれらを組み合わせて得られる炭素数７～１８の基であり、カルボニル基、エステル結合、エーテル結合又はヒドロキシ基を含んでいてもよい。
Ｘ²は、それぞれ独立に、単結合又は－Ｘ²¹－Ｃ(＝Ｏ)－Ｏ－であり、Ｘ²¹は、ヘテロ原子を含んでいてもよい炭素数１～２０のヒドロカルビレン基である。
Ｘ³は、それぞれ独立に、単結合、メチレン基、エチレン基、フェニレン基、フッ素化フェニレン基、トリフルオロメチル基で置換されたフェニレン基、－Ｏ－Ｘ³¹－、－Ｃ(＝Ｏ)－Ｏ－Ｘ³¹－又は－Ｃ(＝Ｏ)－ＮＨ－Ｘ³¹－であり、Ｘ³¹は、炭素数１～６の脂肪族ヒドロカルビレン基、フェニレン基、フッ素化フェニレン基、トリフルオロメチル基で置換されたフェニレン基又はこれらを組み合わせて得られる炭素数７～２０の基であり、カルボニル基、エステル結合、エーテル結合又はヒドロキシ基を含んでいてもよい。
Ｘ⁴は、それぞれ独立に、単結合又はヘテロ原子を含んでいてもよい炭素数１～３０のヒドロカルビレン基である。
ｆ１及びｆ２は、それぞれ独立に、０又は１であるが、Ｘ⁴が単結合のとき、ｆ１及びｆ２は、０である。
Ｒ³¹～Ｒ⁴⁸は、それぞれ独立に、ハロゲン原子、又はヘテロ原子を含んでいてもよい炭素数１～２０のヒドロカルビル基である。また、Ｒ³¹及びＲ³²が、互いに結合してこれらが結合する硫黄原子と共に環を形成してもよく、Ｒ³³及びＲ³⁴、Ｒ³⁶及びＲ³⁷、又はＲ³⁹及びＲ⁴⁰が、互いに結合してこれらが結合する硫黄原子と共に環を形成してもよい。
Ｒ^HFは、水素原子又はトリフルオロメチル基である。
Ｘａ^-は、非求核性対向イオンである。）
８．４～７のいずれかのポリマーを含むベースポリマーを含む化学増福ネガ型レジスト組成物。
９．前記ベースポリマーに含まれるポリマーの全繰り返し単位中、芳香環骨格を有する繰り返し単位の含有率が、６０モル％以上である８の化学増幅ネガ型レジスト組成物。
１０．更に、（Ｂ）酸発生剤を含む８又は９の化学増幅ネガ型レジスト組成物。
１１．更に、（Ｃ）架橋剤を含む８～１０のいずれかの化学増幅ネガ型レジスト組成物。
１２．架橋剤を含まない８～１０のいずれかの化学増幅ネガ型レジスト組成物。
１３．更に、（Ｄ）下記式（Ｄ１）で表される繰り返し単位、下記式（Ｄ２）で表される繰り返し単位、下記式（Ｄ３）で表される繰り返し単位及び下記式（Ｄ４）で表される繰り返し単位から選ばれる少なくとも１種を含み、更に下記式（Ｄ５）で表される繰り返し単位及び下記式（Ｄ６）で表される繰り返し単位から選ばれる少なくとも１種を含んでいてもよいフッ素原子含有ポリマーを含む８～１２のいずれかの化学増幅ネガ型レジスト組成物。

（式中、ｘは、１～３の整数である。ｙは、０≦ｙ≦５＋２ｚ－ｘを満たす整数である。ｚは、０又は１である。ｇは、１～３の整数である。
Ｒ^Cは、それぞれ独立に、水素原子、フッ素原子、メチル基又はトリフルオロメチル基である。
Ｒ^Dは、それぞれ独立に、水素原子又はメチル基である。
Ｒ¹⁰¹、Ｒ¹⁰²、Ｒ¹⁰⁴及びＲ¹⁰⁵は、それぞれ独立に、水素原子又は炭素数１～１０の飽和ヒドロカルビル基である。
Ｒ¹⁰³、Ｒ¹⁰⁶、Ｒ¹⁰⁷及びＲ¹⁰⁸は、それぞれ独立に、水素原子、炭素数１～１５のヒドロカルビル基、炭素数１～１５のフッ素化ヒドロカルビル基又は酸不安定基であり、Ｒ¹⁰³、Ｒ¹⁰⁶、Ｒ¹⁰⁷及びＲ¹⁰⁸がヒドロカルビル基又はフッ素化ヒドロカルビル基のとき、炭素－炭素結合間に、エーテル結合又はカルボニル基が介在していてもよい。
Ｒ¹⁰⁹は、水素原子、又は炭素－炭素結合間にヘテロ原子を含む基が介在していてもよい直鎖状若しくは分岐状の炭素数１～５のヒドロカルビル基である。
Ｒ¹¹⁰は、炭素－炭素結合間にヘテロ原子を含む基が介在していてもよい直鎖状又は分岐状の炭素数１～５のヒドロカルビル基である。
Ｒ¹¹¹は、少なくとも１つの水素原子がフッ素原子で置換された炭素数１～２０の飽和ヒドロカルビル基であり、前記飽和ヒドロカルビル基の－ＣＨ₂－の一部が、エステル結合又はエーテル結合で置換されていてもよい。
Ｚ¹は、炭素数１～２０の(ｇ＋１)価の炭化水素基又は炭素数１～２０の(ｇ＋１)価のフッ素化炭化水素基である。
Ｚ²は、単結合、*－Ｃ(＝Ｏ)－Ｏ－又は*－Ｃ(＝Ｏ)－ＮＨ－である。
Ｚ³は、単結合、－Ｏ－、*－Ｃ(＝Ｏ)－Ｏ－Ｚ³¹－Ｚ³²－又は*－Ｃ(＝Ｏ)－ＮＨ－Ｚ³¹－Ｚ³²－である。Ｚ³¹は、単結合又は炭素数１～１０の飽和ヒドロカルビレン基である。Ｚ³²は、単結合、エステル結合、エーテル結合又はスルホンアミド結合である。
*は、主鎖の炭素原子との結合手である。）
１４．更に、（Ｅ）クエンチャーを含む８～１３のいずれかのネガ型レジスト組成物。
１５．更に、（Ｆ）有機溶剤を含む８～１４のいずれかの化学増幅ネガ型レジスト組成物。
１６．８～１５のいずれかの化学増幅ネガ型レジスト組成物を用いて基板上にレジスト膜を形成する工程、高エネルギー線を用いて前記レジスト膜にパターンを照射する工程、及びアルカリ現像液を用いて前記パターンを照射したレジスト膜を現像する工程を含むレジストパターン形成方法。
１７．前記高エネルギー線が、極端紫外線又は電子線である１６のレジストパターン形成方法。
１８．前記基板の最表面が、クロム、ケイ素、タンタル、モリブデン、コバルト、ニッケル、タングステン及びスズから選ばれる少なくとも１種を含む材料からなる１６又は１７のレジストパターン形成方法。
１９．前記基板が、透過型又は反射型マスクブランクである１６～１８のいずれかのレジストパターン形成方法。
２０．８～１５のいずれかの化学増幅ネガ型レジスト組成物を塗布した透過型又は反射型マスクブランク。 That is, the present invention provides the following monomer, polymer, chemically amplified negative resist composition, and pattern forming method.
1. A monomer represented by the following formula (A1):

(In the formula, a is an integer of 0 to 4.
R ^A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.
L ^A is —O— or —NH—.
L ^B is a single bond, an ether bond, an ester bond or an amide bond.
X ^L is a single bond or a hydrocarbylene group having 1 to 40 carbon atoms which may contain a heteroatom.
R ¹ is a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom.
R ² and R ³ are each independently a hydrogen atom, a saturated hydrocarbyl group having 1 to 15 carbon atoms, or an aryl group having 6 to 15 carbon atoms, the hydrocarbyl group may be substituted with a hydroxy group or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, and the aryl group may have a substituent. However, R ² and R ³ cannot be hydrogen atoms at the same time. R ² and R ³ may be bonded to each other to form a ring together with the carbon atom to which they are bonded, and a portion of -CH ₂ - of the ring may be substituted with -O- or -S-.
W ¹ is a hydrogen atom, an aliphatic hydrocarbyl group having 1 to 10 carbon atoms, an aliphatic hydrocarbylcarbonyl group having 2 to 10 carbon atoms, or an aryl group having 6 to 15 carbon atoms, and the aryl group may have a substituent.
2. A monomer represented by the following formula (A1-1):

(In the formula, a, R ^A , L ^A , R ¹ , R ² , R ³ and W ¹ are the same as defined above.)
3. A monomer 2 represented by the following formula (A1-2):

(In the formula, a, R ^A , L ^A , R ¹ , R ² and R ³ are the same as defined above.)
4. A polymer containing a repeating unit derived from any one of the monomers 1 to 3.
5. The polymer according to 4, further comprising a repeating unit represented by the following formula (A2):

(In the formula, b1 is 0 or 1. b2 is an integer from 0 to 2. b3 is an integer that satisfies 0≦b3≦5+2(b2)−b4. b4 is an integer from 1 to 3.
R ^A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.
R ¹¹ is a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom.
A ¹ is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and a part of the —CH ₂ — in the saturated hydrocarbylene group may be substituted with —O—.
6. The polymer of 4 or 5, further comprising at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (A3), a repeating unit represented by the following formula (A4), and a repeating unit represented by the following formula (A5):

(In the formula, c and d are each independently an integer of 0 to 4. e1 is 0 or 1. e2 is an integer of 0 to 2. e3 is an integer of 0 to 5.
R ^A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.
R ²¹ and R ²² each independently represent a hydroxy group, a halogen atom, a saturated hydrocarbyl group having 1 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 8 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom.
R ²³ is a saturated hydrocarbyl group having 1 to 20 carbon atoms, a saturated hydrocarbyloxy group having 1 to 20 carbon atoms, a saturated hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms, a saturated hydrocarbyloxyhydrocarbyl group having 2 to 20 carbon atoms, a saturated hydrocarbylthiohydrocarbyl group having 2 to 20 carbon atoms, a halogen atom, a nitro group, a cyano group, a saturated hydrocarbylsulfinyl group having 1 to 20 carbon atoms, or a saturated hydrocarbylsulfonyl group having 1 to 20 carbon atoms.
^A2 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and a part of the _--CH2-- of the saturated hydrocarbylene group may be substituted with --O--.
7. The polymer according to any one of 4 to 6, further comprising at least one repeating unit selected from those represented by the following formulae (A6) to (A13):

(In the formula, each R ^B independently represents a hydrogen atom or a methyl group.
X ¹ 's are each independently a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, -O-X ¹¹ -, -C(═O)-O-X ¹¹ -, or -C(═O)-NH-X ¹¹ -, and X ¹¹ is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group.
Each X ² is independently a single bond or —X ²¹ —C(═O)—O—, and X ²¹ is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom.
Each ^X3 is independently a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, -O- ^X31- , -C(=O)-O- ^X31- or -C(=O)-NH- ^X31- , and ^X31 is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group or a group having 7 to 20 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond or a hydroxy group.
Each X ⁴ is independently a single bond or a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom.
f1 and f2 each independently represent 0 or 1, provided that when X ⁴ is a single bond, f1 and f2 are 0.
R ³¹ to R ⁴⁸ are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. R ³¹ and R ³² may be bonded to each other to form a ring together with the sulfur atom to which they are bonded, and R ³³ and R ³⁴ , R ³⁶ and R ³⁷ , or R ³⁹ and R ⁴⁰ may be bonded to each other to form a ring together with the sulfur atom to which they are bonded.
R ^HF is a hydrogen atom or a trifluoromethyl group.
^Xa- is a non-nucleophilic counter ion.
8. A chemically amplified negative resist composition comprising a base polymer comprising any one of the polymers described in 4 to 7.
9. The chemically amplified negative resist composition according to 8, wherein the content of repeating units having an aromatic ring skeleton in all repeating units of the polymer contained in the base polymer is 60 mol % or more.
10. The chemically amplified negative resist composition according to 8 or 9, further comprising (B) an acid generator.
11. The chemically amplified negative resist composition according to any one of 8 to 10, further comprising (C) a crosslinking agent.
12. The chemically amplified negative resist composition according to any one of 8 to 10, which does not contain a crosslinking agent.
13. The chemically amplified negative resist composition according to any one of 8 to 12, further comprising (D) a fluorine atom-containing polymer which contains at least one selected from the group consisting of a repeating unit represented by the following formula (D1), a repeating unit represented by the following formula (D2), a repeating unit represented by the following formula (D3), and a repeating unit represented by the following formula (D4), and which may further contain at least one selected from the group consisting of a repeating unit represented by the following formula (D5) and a repeating unit represented by the following formula (D6):

(In the formula, x is an integer of 1 to 3. y is an integer satisfying 0≦y≦5+2z−x. z is 0 or 1. g is an integer of 1 to 3.
Each R ^C independently represents a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.
Each R ^D independently represents a hydrogen atom or a methyl group.
R ¹⁰¹ , R ¹⁰² , R ¹⁰⁴ and R ¹⁰⁵ each independently represent a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms.
R ¹⁰³ , R ¹⁰⁶ , R ¹⁰⁷ and R ¹⁰⁸ each independently represent a hydrogen atom, a hydrocarbyl group having 1 to 15 carbon atoms, a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, or an acid labile group, and when R ¹⁰³ , R ¹⁰⁶ , R ¹⁰⁷ and R ¹⁰⁸ are a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be present between the carbon-carbon bonds.
R ¹⁰⁹ is a hydrogen atom or a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a heteroatom-containing group interposed between its carbon-carbon bonds.
R ¹¹⁰ is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a heteroatom-containing group interposed between its carbon-carbon bonds.
R ¹¹¹ is a saturated hydrocarbyl group having 1 to 20 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom, and a portion of the --CH ₂ -- in the saturated hydrocarbyl group may be substituted with an ester bond or an ether bond.
Z ¹ is a (g+1)-valent hydrocarbon group having 1 to 20 carbon atoms or a (g+1)-valent fluorinated hydrocarbon group having 1 to 20 carbon atoms.
^Z2 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-.
Z ³ is a single bond, --O--, *-C(=O)--O--Z ³¹ -Z ³² - or *-C(=O)--NH--Z ³¹ -Z ³² -. Z ³¹ is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms. Z ³² is a single bond, an ester bond, an ether bond or a sulfonamide bond.
* indicates a bond to a carbon atom in the main chain.)
14. The negative resist composition according to any one of 8 to 13, further comprising (E) a quencher.
15. The chemically amplified negative resist composition according to any one of 8 to 14, further comprising (F) an organic solvent.
16. A method for forming a resist pattern, comprising the steps of forming a resist film on a substrate using the chemically amplified negative resist composition according to any one of claims 8 to 15, irradiating the resist film with a pattern using high-energy rays, and developing the resist film irradiated with the pattern using an alkaline developer.
17. The method for forming a resist pattern according to 16, wherein the high-energy radiation is extreme ultraviolet radiation or an electron beam.
18. The method for forming a resist pattern according to 16 or 17, wherein the outermost surface of the substrate is made of a material containing at least one selected from the group consisting of chromium, silicon, tantalum, molybdenum, cobalt, nickel, tungsten and tin.
19. The method for forming a resist pattern according to any one of 16 to 18, wherein the substrate is a transmission type or a reflection type mask blank.
20. A transmission or reflection mask blank coated with any one of the chemically amplified negative resist compositions described in any one of 8 to 15.

When a pattern is formed using a chemically amplified negative resist composition containing a polymer obtained from the monomer of the present invention as a base polymer, a polarity change accompanied by a dehydration reaction proceeds with good sensitivity, and a pattern can be formed with high resolution and pattern fidelity while improving LER and dose margin, making it suitable for use in microfabrication techniques, particularly EUV lithography and EB lithography.

The present invention is described in detail below, but is not limited thereto. In the following description, some structures represented by chemical formulas may have asymmetric carbons and may have enantiomers or diastereomers, and in such cases, a single formula will be used to represent these isomers. These isomers may be used alone or as a mixture.

[monomer]
The monomer of the present invention is represented by the following formula (A1).

In formula (A1), a is an integer from 0 to 4, preferably 0 or 1.

In formula (A1), R ^A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group, and among these, a hydrogen atom or a methyl group is preferable.

In formula (A1), L ^A is —O— or —NH—, and among these, —O— is preferable.

In formula (A1), L ^B is a single bond, an ether bond, an ester bond or an amide bond, among which a single bond, an ether bond or an ester bond is preferred.

In formula (A1), X ^L is a single bond or a hydrocarbylene group having 1 to 40 carbon atoms which may contain a heteroatom. The hydrocarbylene group may be linear, branched, or cyclic, and specific examples thereof include an alkanediyl group having 1 to 40 carbon atoms and a cyclic saturated hydrocarbylene group having 3 to 40 carbon atoms. Specific examples of the heteroatom include an oxygen atom, a nitrogen atom, and a sulfur atom.

Specific examples of the hydrocarbylene group having 1 to 40 carbon atoms which may contain a heteroatom represented by X ^L include, but are not limited to, those shown below. In the following formula, * represents a bond to L ^A and L ^B , respectively.

Of these, X ^L -0 to X ^L -22 and X ^L -47 to X ^L -49 are preferred, and X ^L -0 to X ^L -17 are more preferred.

In formula (A1), R ¹ is a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom.

Specific examples of the halogen atom represented by R ¹ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

The hydrocarbyl group having 1 to 20 carbon atoms represented by R ¹ may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, tert-pentyl, n-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclic saturated hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, tricyclo[5.2.1.0 ^2,6 ]decyl, adamantyl, and adamantylmethyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, naphthyl, and anthryl; and groups obtained by combining these. In addition, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the _-CH2- of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a carbamate bond, an amide bond, an imide bond, a lactone ring, a sultone ring, a thiolactone ring, a lactam ring, a sultam ring, a carboxylic anhydride (-C(=O)-O-C(=O)-), a haloalkyl group, etc.

In formula (A1), ^R2 and ^R3 each independently represent a hydrogen atom, a saturated hydrocarbyl group having 1 to 15 carbon atoms, or an aryl group having 6 to 15 carbon atoms, the hydrocarbyl group optionally being substituted with a hydroxy group or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, and the aryl group optionally having a substituent.

The saturated hydrocarbyl group having 1 to 15 carbon atoms represented by ^R2 and ^R3 may be linear, branched or cyclic. Specific examples thereof include alkyl groups having 1 to 15 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, 2-ethylhexyl, n-octyl, n-nonyl and n-decyl groups; and cyclic saturated hydrocarbyl groups having 3 to 15 carbon atoms, such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl and adamantyl groups.

Specific examples of the aryl group having 6 to 15 carbon atoms represented by ^R2 and ^R3 include a phenyl group, a naphthyl group, an anthryl group, etc., of which a phenyl group is preferred. The aryl group may have a substituent, and specific examples of the substituent include a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, etc.

In addition, ^R2 and ^R3 cannot be hydrogen atoms at the same time. When either ^R2 or ^R3 is an aryl group which may have a substituent, the other substituent is preferably a hydrogen atom.

It is preferable that R ² and R ³ are the same group, and it is more preferable that both are methyl groups.

^R2 and ^R3 may be bonded to each other to form a ring together with the carbon atom to which they are bonded, and a part of _-CH2- in the ring may be replaced by -O- or -S-. Examples of the ring include a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a norbornane ring, an adamantane ring, a tricyclo[ ^5.2.1.02,6 ]decane ring, ^a tetracyclo[ ^{6.2.1.13,6.02,7} ]dodecane ring, an oxanorbornane ring, a thianorbornane ring, and the like, but are not limited thereto.

In formula (A1), W ¹ is a hydrogen atom, an aliphatic hydrocarbyl group having 1 to 10 carbon atoms, an aliphatic hydrocarbylcarbonyl group having 2 to 10 carbon atoms, or an aryl group having 6 to 15 carbon atoms, and the aryl group may have a substituent.

The aliphatic hydrocarbyl group having 1 to 10 carbon atoms represented by W ¹ may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 10 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, neopentyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclic saturated hydrocarbyl groups having 3 to 10 carbon atoms, such as cyclopentyl and cyclohexyl; alkenyl groups having 2 to 10 carbon atoms, such as vinyl, 1-propenyl, 2-propenyl, butenyl, and hexenyl; and cyclic unsaturated hydrocarbyl groups having 3 to 10 carbon atoms, such as cyclohexenyl. Specific examples of the aryl group having 6 to 15 carbon atoms represented by ^W1 include a phenyl group, a naphthyl group, an anthryl group, etc., among which a phenyl group is preferable. The aryl group may have a substituent, and specific examples of the substituent include a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, etc.

W ¹ is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, further preferably a hydrogen atom or a methyl group, and most preferably a hydrogen atom.

（式中、ａ、Ｒ^A、Ｌ^A、Ｒ¹、Ｒ²、Ｒ³及びＷ¹は、前記と同じ。） The monomer represented by formula (A1) is preferably one represented by the following formula (A1-1).

(In the formula, a, R ^A , L ^A , R ¹ , R ² , R ³ and W ¹ are the same as defined above.)

（式中、ａ、Ｒ^A、Ｌ^A、Ｒ¹、Ｒ²及びＲ³は、前記と同じ。） The monomer represented by formula (A1-1) is further preferably one represented by the following formula (A1-2).

(In the formula, a, R ^A , L ^A , R ¹ , R ² and R ³ are the same as defined above.)

Specific examples of the monomer represented by formula (A1) include, but are not limited to, those shown below: In the following formula, R ^A is the same as above, Me is a methyl group, and Ac is an acetyl group.

（式中、ａ、Ｒ^A、Ｒ¹、Ｒ²、Ｌ^A及びＸ^Lは、前記と同じ。Ｒ^xは、炭素数１～１０のヒドロカルビル基である。Ｘ^halは、塩素原子、臭素原子又はヨウ素原子である。） The monomer of the present invention can be synthesized by a known method. As an example, a monomer A1-ex in which L ^B is an ester bond, R ² and R ³ are the same group, and W ¹ is a hydrogen atom in the above formula (A) will be described, but the synthesis method is not limited thereto.

(In the formula, a, R ^A , R ¹ , R ² , L ^A and X ^L are the same as defined above. R ^x is a hydrocarbyl group having 1 to 10 carbon atoms. X ^hal is a chlorine atom, a bromine atom or an iodine atom.)

The first step is to react a Grignard reagent with an ester compound SM-1 or a ketone compound SM-2, which are commercially available or can be synthesized by a known synthesis method, to obtain Pre-A1-ex, which is a precursor diol compound.

The reaction can be carried out by a known organic synthesis method. Specifically, metallic magnesium is suspended in an ether solvent such as tetrahydrofuran (THF) or diethyl ether, and a halide diluted with the solvent used is added dropwise to prepare a Grignard reagent. When preparing a Grignard reagent, especially when the halide is a chloride, the reaction can be efficiently started by adding a small amount of 1,2-dibromoethane or iodine before starting the dropwise addition of the halide. The ester compound SM-1 or the ketone compound SM-2 diluted with the solvent used is added dropwise to the prepared Grignard reagent. The reaction temperature is from room temperature to the boiling point of the solvent used. The reaction time is usually about 30 minutes to 2 hours, although it is desirable to follow the reaction by gas chromatography (GC) or silica gel thin layer chromatography (TLC) to complete the reaction in terms of yield. The precursor diol compound Pre-A1-ex can be obtained from the reaction mixture by a normal aqueous work-up. If necessary, the resulting monomer precursor Pre-A1-ex can be purified by conventional methods such as distillation, chromatography, and recrystallization.

The second step is to introduce a polymerizable group via an ester bond into the diol compound Pre-A1-ex obtained in the first step to obtain the monomer A1-ex.

The reaction can be carried out by a known organic synthesis method. Specifically, Pre-A1-ex is dissolved in a solvent such as toluene, hexane, THF, or acetonitrile in the presence of an organic base such as triethylamine or pyridine, and an acid halide such as methacrylic acid chloride or acrylic acid chloride is added dropwise to carry out the reaction. 4-Dimethylaminopyridine may be added to accelerate the reaction rate. The reaction temperature is from 5°C to the boiling point of the solvent used. The reaction time is usually about 1 to 24 hours, although it is desirable to follow the reaction by GC or TLC and complete the reaction in terms of yield. Monomer A1-ex can be obtained from the reaction mixture by a normal aqueous work-up. The obtained monomer A1-ex can be purified by a normal method such as distillation, chromatography, or recrystallization, if necessary.

The structural feature of the monomer of the present invention is that an acid dehydrating group (or acid leaving group) is attached to the meta position from the carbon atom to which the polymerizable group on the benzene ring is attached. The acid dehydrating group (acid leaving group) reacts with the acid generated from the acid generator to cause a dehydration reaction (elimination reaction) and generate a benzyl cation. The hydrogen atom in the vicinity is released as a proton, forming an olefin structure conjugated with the benzene ring, which becomes hydrophobic. Alternatively, the hydrophobicity is improved by a nucleophilic attack of a phenolic hydroxy group in the copolymerized polymer chain on the generated benzyl cation. If this functional group is located in the para position from the carbon atom to which the polymerizable group of the aromatic ring is attached, the reactivity to acid is too high, so the functional group in the unexposed area also undergoes a dehydration reaction (elimination reaction), and the contrast between the exposed and unexposed areas decreases. In addition, if multiple functional groups are attached to the benzene ring, the dehydration reaction (elimination reaction) does not proceed sufficiently, and it is thought that a structure in which an olefin structure and an alcohol structure coexist is also generated in some exposed areas. Therefore, if the exposed portion is developed with an alkaline developer in this state, the hydrophilic alcohol structure remains, which attracts water from the developer, resulting in a deterioration of the pattern shape. The monomer of the present invention has an acid dehydrating group (or an acid leaving group) at the meta position of the benzene ring, which has moderate reactivity, and therefore can form a negative pattern with a high dissolution contrast between the exposed and unexposed portions and a good pattern shape.

[polymer]
The polymer of the present invention contains a repeating unit derived from the above-mentioned monomer (hereinafter referred to as repeating unit A1).

The polymer may further include a repeating unit represented by the following formula (A2) (hereinafter, also referred to as repeating unit A2): The repeating unit A2 is a repeating unit that imparts etching resistance, adhesion to a substrate, and solubility in an alkaline developer.

In formula (A2), b1 is 0 or 1. b2 is an integer from 0 to 2, and when it is 0, it represents a benzene skeleton, when it is 1, it represents a naphthalene skeleton, and when it is 2, it represents an anthracene skeleton. b3 is an integer satisfying 0≦b3≦5+2(b2)-b4. b4 is an integer from 1 to 3. When b2 is 0, preferably b3 is an integer from 0 to 3 and b4 is an integer from 1 to 3, and when b2 is 1 or 2, preferably b3 is an integer from 0 to 4 and b4 is an integer from 1 to 3.

In formula (A2), R ^A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

In formula (A2), R ¹¹ is a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom. The saturated hydrocarbyl group, and the saturated hydrocarbyl part of the saturated hydrocarbyloxy group and the saturated hydrocarbylcarbonyloxy group may be linear, branched, or cyclic, and specific examples thereof include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl, and structural isomers thereof; cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl; and groups obtained by combining these groups. If the number of carbon atoms is equal to or less than the upper limit, the solubility in an alkaline developer is good. When b3 is 2 or more, each R ¹¹ may be the same as or different from each other.

In formula (A2), A ¹ is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and a portion of the —CH ₂ — in the saturated hydrocarbylene group may be substituted with —O—. The saturated hydrocarbylene group may be linear, branched, or cyclic, and specific examples thereof include alkanediyl groups having 1 to 10 carbon atoms, such as methylene, ethane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, and hexane-1,6-diyl groups, and structural isomers thereof; cyclic saturated hydrocarbylene groups having 3 to 10 carbon atoms, such as cyclopropanediyl, cyclobutanediyl, cyclopentanediyl, and cyclohexanediyl groups; and groups obtained by combining these groups. When the saturated hydrocarbylene group contains an ether bond, when b1 in formula (A2) is 1, the ether bond may be inserted at any position except between the carbon atom at the α-position and the carbon atom at the β-position relative to the ester oxygen atom. When b1 is 0, the atom bonded to the main chain is an ether oxygen atom, and the second ether bond may be inserted at any position except between the carbon atom at the α-position and the carbon atom at the β-position relative to the ether oxygen atom. It is preferable that the saturated hydrocarbylene group has 10 or less carbon atoms, since sufficient solubility in an alkaline developer can be obtained.

（式中、Ｒ^A及びｂ４は、前記と同じ。） When b1 is 0 and A ¹ is a single bond, that is, when the aromatic ring is directly bonded to the main chain of the polymer (i.e., there is no linker (-C(═O)-O-A ¹ -)), preferred examples of the repeating unit A2 include units derived from 3-hydroxystyrene, 4-hydroxystyrene, 5-hydroxy-2-vinylnaphthalene, 6-hydroxy-2-vinylnaphthalene, etc. In particular, the repeating unit represented by the following formula (A2-1) is preferred.

(In the formula, ^R and b4 are the same as above.)

（式中、Ｒ^Aは、前記と同じ。） Furthermore, when b1 is 1 (that is, the repeating unit A2 has --C(.dbd.O)--O-- ^A.sub.1-- as a linker), preferred examples of the repeating unit A2 include, but are not limited to, those shown below.

(In the formula, ^R is the same as above.)

Repeating unit A2 may be used alone or in combination of two or more types.

For the purpose of improving etching resistance, the polymer may contain at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (A3) (hereinafter also referred to as repeating unit A3), a repeating unit represented by the following formula (A4) (hereinafter also referred to as repeating unit A4), and a repeating unit represented by the following formula (A5) (hereinafter also referred to as repeating unit A5).

In formulas (A3) and (A4), c and d are each independently an integer from 0 to 4.

In formulas (A3) and (A4), R ²¹ and R ²² are each independently a hydroxy group, a halogen atom, a saturated hydrocarbyl group having 1 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 8 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom. The saturated hydrocarbyl group, saturated hydrocarbyloxy group, and saturated hydrocarbylcarbonyloxy group may be linear, branched, or cyclic. When c is 2 or more, each R ²¹ may be the same as or different from each other. When d is 2 or more, each R ²² may be the same as or different from each other.

In formula (A5), e1 is 0 or 1. e2 is an integer from 0 to 2, and when e2 is 0, it represents a benzene skeleton, when e2 is 1, it represents a naphthalene skeleton, and when e2 is 2, it represents an anthracene skeleton. e3 is an integer from 0 to 5. When e2 is 0, e3 is preferably an integer from 0 to 3, and when e2 is 1 or 2, e3 is preferably an integer from 0 to 4.

In formula (A5), R ^A represents a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

In formula (A5), R ²³ is a saturated hydrocarbyl group having 1 to 20 carbon atoms, a saturated hydrocarbyloxy group having 1 to 20 carbon atoms, a saturated hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms, a saturated hydrocarbyloxyhydrocarbyl group having 2 to 20 carbon atoms, a saturated hydrocarbylthiohydrocarbyl group having 2 to 20 carbon atoms, a halogen atom, a nitro group, a cyano group, a saturated hydrocarbylsulfinyl group having 1 to 20 carbon atoms, or a saturated hydrocarbylsulfonyl group having 1 to 20 carbon atoms. The saturated hydrocarbyl group, saturated hydrocarbyloxy group, saturated hydrocarbylcarbonyloxy group, saturated hydrocarbyloxyhydrocarbyl group, saturated hydrocarbylthiohydrocarbyl group, saturated hydrocarbylsulfinyl group, and saturated hydrocarbylsulfonyl group may be linear, branched, or cyclic. When e3 is 2 or more, each R ²³ may be the same as or different from each other.

^R23 is preferably a halogen atom such as a chlorine atom, a bromine atom, or an iodine atom; a saturated hydrocarbyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a cyclopentyl group, a cyclohexyl group, or a structural isomer thereof; or a saturated hydrocarbyloxy group such as a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a cyclopentyloxy group, a cyclohexyloxy group, or a structural isomer thereof. Of these, a methoxy group and an ethoxy group are particularly useful.

In addition, the saturated hydrocarbyl carbonyloxy group can be easily introduced by a chemical modification method even after polymerization of the polymer, and can be used to finely adjust the solubility of the base polymer in an alkaline developer. Examples of the saturated hydrocarbyl carbonyloxy group include methyl carbonyloxy group, ethyl carbonyloxy group, propyl carbonyloxy group, butyl carbonyloxy group, pentyl carbonyloxy group, hexyl carbonyloxy group, cyclopentyl carbonyloxy group, cyclohexyl carbonyloxy group, benzoyloxy group, and structural isomers of the hydrocarbon portion of these groups. If the number of carbon atoms is 20 or less, the effect of controlling and adjusting (mainly the effect of reducing) the solubility of the base polymer in an alkaline developer can be made appropriate, and the occurrence of scum (development defects) can be suppressed.

Among the preferred substituents mentioned above, examples of substituents that are particularly easy to prepare as monomers and are useful include chlorine atoms, bromine atoms, iodine atoms, methyl groups, ethyl groups, and methoxy groups.

In formula (A5), ^A2 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and a part of the _-CH2- of the saturated hydrocarbylene group may be replaced by -O-. The saturated hydrocarbylene group may be linear, branched, or cyclic, and specific examples thereof include alkanediyl groups having 1 to 10 carbon atoms, such as methylene, ethane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, and structural isomers thereof; cyclic saturated hydrocarbylene groups having 3 to 10 carbon atoms, such as cyclopropanediyl, cyclobutanediyl, cyclopentanediyl, and cyclohexanediyl; and groups obtained by combining these. When the saturated hydrocarbylene group contains an ether bond, when e1 in formula (A5) is 1, the ether bond may be inserted at any position except between the carbon atom at the α-position and the carbon atom at the β-position relative to the ester oxygen atom. When e1 is 0, the atom bonded to the main chain is an ether oxygen atom, and the second ether bond may be inserted at any position except between the carbon atom at the α-position and the carbon atom at the β-position relative to the ether oxygen atom. If the carbon number of the saturated hydrocarbylene group is 10 or less, sufficient solubility in an alkaline developer can be obtained, which is preferable.

When e1 is 0 and ^A2 is a single bond, that is, when the aromatic ring is directly bonded to the main chain of the polymer (i.e., there is no linker (-C(=O)-O- ^A3- )), preferred examples of the repeating unit A5 include units derived from styrene, 4-chlorostyrene, 4-methylstyrene, 4-methoxystyrene, 4-bromostyrene, 4-acetoxystyrene, 2-hydroxypropylstyrene, 2-vinylnaphthalene, 3-vinylnaphthalene, etc.

Furthermore, when e1 is 1 (i.e., when the linker is --C(.dbd.O)--O-- ^A.sub.2-- ), preferred examples of the repeating unit A5 include, but are not limited to, those shown below. In the following formula, ^R.sub.A is the same as defined above.

When at least one of the repeating units A3 to A5 is used as a structural unit of the polymer, the addition of a ring structure to the main chain provides the effect of improving the etching resistance of the aromatic ring as well as the resistance to EB irradiation during pattern inspection.

Repeating units A3 to A5 may be used alone or in combination of two or more.

The polymer may further include at least one selected from the repeating unit represented by the following formula (A6) (hereinafter also referred to as repeating unit A6), the repeating unit represented by the following formula (A7) (hereinafter also referred to as repeating unit A7), the repeating unit represented by the following formula (A8) (hereinafter also referred to as repeating unit A8), the repeating unit represented by the following formula (A9) (hereinafter also referred to as repeating unit A9), the repeating unit represented by the following formula (A10) (hereinafter also referred to as repeating unit A10), the repeating unit represented by the following formula (A11) (hereinafter also referred to as repeating unit A11), the repeating unit represented by the following formula (A12) (hereinafter also referred to as repeating unit A12), and the repeating unit represented by the following formula (A13) (hereinafter also referred to as repeating unit A13). In this case, acid diffusion can be effectively suppressed, and a pattern with improved resolution and reduced LER can be obtained.

In formulae (A6) to (A13), R ^B is independently a hydrogen atom or a methyl group. Each X ¹ is independently a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, -O-X ¹¹ -, -C(═O)-O-X ¹¹ -, or -C(═O)-NH-X ¹¹ -, where X ¹¹ is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. Each X ² is independently a single bond or -X ²¹ -C(═O)-O-, where X ²¹ is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. X ³ is each independently a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, -O-X ³¹ -, -C(=O)-O-X ³¹ - or -C(=O)-NH-X ³¹ -, and X ³¹ is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, or a group having 7 to 20 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxyl group. X ⁴ is each independently a single bond or a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom. f1 and f2 are each independently 0 or 1, and when X ⁴ is a single bond, f1 and f2 are 0.

In formulae (A6) and (A10), Xa ⁻ is a non-nucleophilic counter ion. Examples of the non-nucleophilic counter ion represented by Xa ⁻ include those described in JP-A Nos. 2010-113209 and 2007-145797.

（式中、破線は、結合手である。） In formulas (A7) and (A11), when X ² is —X ²¹ —C(═O)—O—, examples of the hydrocarbylene group which may contain a heteroatom represented by X ²¹ include, but are not limited to, the following:

(In the formula, the dashed lines represent bonds.)

In formulae (A7) and (A11), R ^HF is a hydrogen atom or a trifluoromethyl group. In the repeating units A7 and A11, specific examples of the repeating units in which R ^HF is a hydrogen atom include those described in JP-A-2010-116550, and specific examples of the repeating units in which R ^HF is a trifluoromethyl group include those described in JP-A-2010-77404. Examples of the repeating units A8 and A12 include those described in JP-A-2012-246265 and JP-A-2012-246426.

In formulae (A6) and (A10), Xa ⁻ is a non-nucleophilic counter ion. Examples of the non-nucleophilic counter ion represented by Xa ⁻ include those described in JP-A Nos. 2010-113209 and 2007-145797.

Preferred examples of the anion of the monomer that provides the repeating units A9 and A13 include, but are not limited to, those shown below.

In formulae (A6) to (A13), R ³¹ to R ⁴⁸ are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include the same as those exemplified as the hydrocarbyl group represented by R ¹ in the explanation of formula (A1). In addition, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the _-CH2- of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-O-C(=O)-), a haloalkyl group, etc.

（式中、破線は、結合手である。） In addition, R ³¹ and R ³² may be bonded to each other to form a ring together with the sulfur atom to which they are bonded, and R ³³ and R ³⁴ , R ³⁶ and R ³⁷ , or R ³⁹ and R ⁴⁰ may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. Examples of the ring formed in this case include those represented by the following formula.

(In the formula, the dashed lines represent bonds.)

Specific examples of the sulfonium cations in the repeating units A7 to A9 include, but are not limited to, those shown below.

Specific examples of the iodonium cations in the repeating units A11 to A13 include, but are not limited to, those shown below.

Repeating units A6 to A13 are units that generate acid when irradiated with high-energy rays. It is believed that the inclusion of these units in the polymer appropriately suppresses acid diffusion, making it possible to obtain a pattern with reduced LER. In addition, the inclusion of these units in the polymer suppresses the phenomenon in which acid volatilizes from exposed areas and reattaches to unexposed areas during baking in a vacuum, which is believed to be effective in reducing LER and reducing defects caused by suppressing undesired negative reactions in unexposed areas.

Repeating units A6 to A13 may be used alone or in combination of two or more.

The polymer may contain (meth)acrylic acid ester units or other repeating units having adhesive groups such as lactone structures and hydroxy groups other than phenolic hydroxy groups in order to fine-tune the properties of the resist film.

Examples of the (meth)acrylic acid ester unit having the adhesive group include a repeating unit represented by the following formula (A14) (hereinafter also referred to as repeating unit A14), a repeating unit represented by the following formula (A15) (hereinafter also referred to as repeating unit A15), and a repeating unit represented by the following formula (A16) (hereinafter also referred to as repeating unit A16). These units do not exhibit acidity and can be used auxiliary as units that impart adhesion to a substrate or units that adjust solubility.

In formulae (A14) to (A16), R ^A is each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R ⁵¹ is -O- or a methylene group. R ⁵² is a hydrogen atom or a hydroxy group. R ⁵³ is a saturated hydrocarbyl group having 1 to 4 carbon atoms. k is an integer from 0 to 3. The repeating units A14 to A16 may be used alone or in combination of two or more types.

In the polymer, the content of repeating unit A1 is preferably 5 to 70 mol%, more preferably 10 to 60 mol%, in order to obtain the effect of promoting the negativization reaction. The content of repeating unit A2 is preferably 30 to 95 mol%, more preferably 50 to 85 mol%, in order to obtain high contrast between the part that is negated by high-energy radiation irradiation and the part that is not irradiated (part that is not negated) in order to obtain high resolution. The content of repeating units A3 to A5 is preferably 0 to 30 mol%, more preferably 3 to 20 mol%, in order to obtain the effect of improving etching resistance. Note that other repeating units may be contained in an amount of 0 to 30 mol%, preferably 0 to 20 mol%.

When the polymer does not contain repeating units A6 to A13, the content of repeating unit A2 in the polymer is preferably 25 to 95 mol%, more preferably 40 to 85 mol%. The content of repeating units A3 to A5 is preferably 0 to 30 mol%, more preferably 3 to 20 mol%. The content of repeating unit A5 is preferably 5 to 70 mol%, more preferably 10 to 60 mol%. The polymer may contain other repeating units in an amount of 0 to 30 mol%, preferably 0 to 20 mol%.

When the polymer contains repeating units A6 to A13, the content of repeating unit A2 in the polymer is preferably 25 to 94.5 mol%, more preferably 36 to 85 mol%. The content of repeating units A3 to A5 is preferably 0 to 30 mol%, more preferably 3 to 20 mol%. The content of repeating unit A5 is preferably 5 to 70 mol%, more preferably 10 to 60 mol%. The total content of repeating units A1 to A5 is preferably 60 to 99.5 mol%. The content of repeating units A6 to A13 is preferably 0.5 to 20 mol%, more preferably 1 to 10 mol%. The polymer may contain other repeating units in an amount of 0 to 30 mol%, preferably 0 to 20 mol%.

The polymer can be synthesized by copolymerizing each monomer, which is protected with a protecting group as necessary, by a known method, and then carrying out a deprotection reaction as necessary. The copolymerization reaction is not particularly limited, but is preferably radical polymerization or anionic polymerization. For these methods, reference can be made to WO 2006/121096, JP 2008-102383 A, JP 2008-304590 A, and JP 2004-115630 A.

[Chemically amplified negative resist composition]
The chemically amplified negative resist composition of the present invention contains (A) a base polymer containing the above-mentioned polymer.

In this case, in the polymer, the repeating units A1 to A5 preferably account for 60 mol % or more of the total repeating units, more preferably 70 mol % or more, and even more preferably 80 mol % or more. This ensures that the properties required for the chemically amplified negative resist composition of the present invention are obtained.

The polymer preferably has a weight average molecular weight (Mw) of 1000 to 50000, more preferably 2000 to 20000. If Mw is 1000 or more, there is no risk of the phenomenon of the pattern head becoming rounded, reducing the resolution and deteriorating the LER, as is conventionally known. On the other hand, if Mw is 50000 or less, there is no risk of the LER increasing, especially when forming a pattern with a pattern line width of 100 nm or less. In the present invention, Mw is a polystyrene-equivalent measured value obtained by gel permeation chromatography (GPC).

The polymer preferably has a narrow molecular weight distribution (Mw/Mn) of 1.0 to 2.0, and particularly 1.0 to 1.8. If the polymer has such a narrow distribution, no foreign matter will be produced on the pattern after development, and the shape of the pattern will not deteriorate.

The (A) base polymer may contain two or more polymers with different composition ratios, Mw, and Mw/Mn. In particular, a polymer that does not contain repeating units A6 to A13 may be used in combination with a polymer that contains repeating units A6 to A13. In this case, the content of the polymer that does not contain repeating units A6 to A13 in the chemically amplified negative resist composition of the present invention is preferably 2 to 5,000 parts by mass, and more preferably 10 to 1,000 parts by mass, per 100 parts by mass of the polymer that does not contain repeating units A6 to A13.

When the chemically amplified negative resist composition is used to prepare a mask, the coating thickness in the most advanced generation is 150 nm or less, preferably 100 nm or less. The dissolution rate of the base polymer in an alkaline developer (e.g., a 2.38% by mass aqueous solution of tetramethylammonium hydroxide (TMAH)) is preferably 80 nm/sec or less, more preferably 50 nm/sec or less, in order to form a fine pattern, which is generally a strong development process to reduce defects caused by resist residues. Also, for example, when preparing an LSI chip from a wafer, when the chemically amplified negative resist composition of the present invention is used in an EUV exposure process, it is necessary to pattern fine lines of 50 nm or less, so the coating thickness is often 100 nm or less, and since the pattern may deteriorate due to development due to the thin film, the dissolution rate of the polymer used is preferably 80 nm/sec or less, more preferably 50 nm/sec or less.

[(B) Acid Generator]
The chemically amplified negative resist composition of the present invention may contain an acid generator as component (B). Examples of such acid generators include compounds (photoacid generators) that generate an acid in response to actinic rays or radiation. There are no particular limitations on the photoacid generator, so long as it is a compound that generates an acid upon exposure to high-energy rays. Suitable photoacid generators include sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate-type acid generators.

Specific examples of the photoacid generator include nonafluorobutanesulfonate, the partially fluorinated sulfonates described in paragraphs [0247] to [0251] of JP-A-2012-189977, the partially fluorinated sulfonates described in paragraphs [0261] to [0265] of JP-A-2013-101271, the partially fluorinated sulfonates described in paragraphs [0122] to [0142] of JP-A-2008-111103, and the ones described in paragraphs [0080] to [0081] of JP-A-2010-215608. Among these, arylsulfonate-type or alkane sulfonate-type photoacid generators are preferred because they generate an acid of suitable strength for reacting the crosslinking agent (C) described below with the base polymer (A).

In addition, in order to obtain the effect of improving the LER by combining the photoacid generator with a quencher, component (E), described below, the pKa of the acid generated from the photoacid generator is -3.0 or more, preferably in the range of -3.0 to 2.0, and more preferably in the range of -2.0 to 1.5.

Such an acid generator is preferably a compound having an anion of the structure shown below: Examples of the counter cation include those exemplified as specific examples of the sulfonium cation in the repeating units A7 to A9 and those exemplified as specific examples of the iodonium cation in the repeating units A11 to A13.

When the chemically amplified negative resist composition of the present invention contains the acid generator (B), the content thereof is preferably 1 to 30 parts by mass, and more preferably 2 to 20 parts by mass, relative to 80 parts by mass of the base polymer (A). When the base polymer contains repeating units A6 to A13 (i.e., when it is a polymer-bound acid generator), the incorporation of the acid generator (B) may be omitted. The acid generator (B) may be used alone or in combination of two or more types.

[(C) Crosslinking Agent]
The chemically amplified negative resist composition of the present invention may contain a crosslinking agent as component (C).Specific examples of the crosslinking agent include epoxy compounds, melamine compounds, guanamine compounds, glycoluril compounds or urea compounds, isocyanate compounds, azide compounds, and compounds containing double bonds such as alkenyloxy groups, which are substituted with at least one group selected from methylol groups, alkoxymethyl groups, and acyloxymethyl groups.These may be used as additives, or may be introduced as pendant groups into polymer side chains.Also, compounds containing hydroxyl groups may be used as crosslinking agents.

Examples of the epoxy compound include tris(2,3-epoxypropyl)isocyanurate, trimethylolmethane triglycidyl ether, trimethylolpropane triglycidyl ether, and triethylolethane triglycidyl ether.

Examples of the melamine compounds include compounds in which 1 to 6 methylol groups are methoxymethylated, such as hexamethylol melamine, hexamethoxymethyl melamine, and hexamethylol melamine, or mixtures thereof; and compounds in which 1 to 6 methylol groups are acyloxymethylated, such as hexamethoxyethyl melamine, hexaacyloxymethyl melamine, and hexamethylol melamine, or mixtures thereof.

Examples of the guanamine compound include compounds in which 1 to 4 methylol groups are methoxymethylated, such as tetramethylol guanamine, tetramethoxymethyl guanamine, and tetramethylol guanamine, or mixtures thereof; and compounds in which 1 to 4 methylol groups are acyloxymethylated, such as tetramethoxyethyl guanamine, tetraacyloxy guanamine, and tetramethylol guanamine, or mixtures thereof.

Examples of the glycoluril compound include compounds in which 1 to 4 methylol groups are methoxymethylated, such as tetramethylol glycoluril, tetramethoxymethyl glycoluril, and tetramethylol glycoluril, or mixtures thereof, and compounds in which 1 to 4 methylol groups are acyloxymethylated, such as tetramethylol glycoluril, tetramethoxymethyl glycoluril, and mixtures thereof.

Examples of the urea compounds include tetramethylol urea, tetramethoxymethyl urea, tetramethylol urea, and other compounds in which one to four methylol groups are methoxymethylated, or mixtures thereof, tetramethoxyethyl urea, etc.

Examples of the isocyanate compound include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, etc.

Examples of the azide compound include 1,1'-biphenyl-4,4'-bisazide, 4,4'-methylidenebisazide, and 4,4'-oxybisazide.

Examples of compounds containing the alkenyloxy group include ethylene glycol divinyl ether, triethylene glycol divinyl ether, 1,2-propanediol divinyl ether, 1,4-butanediol divinyl ether, tetramethylene glycol divinyl ether, neopentyl glycol divinyl ether, trimethylolpropane trivinyl ether, hexanediol divinyl ether, 1,4-cyclohexanediol divinyl ether, pentaerythritol trivinyl ether, pentaerythritol tetravinyl ether, sorbitol tetravinyl ether, sorbitol pentavinyl ether, and trimethylolpropane trivinyl ether.

In the chemically amplified negative resist composition of the present invention, the content of the crosslinking agent (C) is preferably 0.1 to 50 parts by mass, more preferably 1 to 30 parts by mass, per 80 parts by mass of the base polymer (A). Within this range, there is little risk of patterns being connected together and the resolution being reduced. The crosslinking agent (C) may be used alone or in combination of two or more types.

[(D) Fluorine Atom-Containing Polymer]
The chemically amplified negative resist composition of the present invention, for the purposes of increasing contrast, suppressing chemical flare of acid upon irradiation with high-energy rays, shielding mixing of acid from an antistatic film in the process of applying an antistatic film material onto a resist film, and suppressing unexpected and unnecessary pattern deterioration, may contain, as the component (D), a fluorine atom-containing polymer that contains at least one selected from a repeating unit represented by the following formula (D1) (hereinafter also referred to as repeating unit D1), a repeating unit represented by the following formula (D2) (hereinafter also referred to as repeating unit D2), a repeating unit represented by the following formula (D3) (hereinafter also referred to as repeating unit D3), and a repeating unit represented by the following formula (D4) (hereinafter also referred to as repeating unit D4), and may further contain at least one selected from a repeating unit represented by the following formula (D5) (hereinafter also referred to as repeating unit D5) and a repeating unit represented by the following formula (D6) (hereinafter also referred to as repeating unit D6). The fluorine atom-containing polymer also functions as a surfactant, and is therefore effective against development defects since it can prevent insoluble matter from re-adhering to the substrate during the development process.

In formulas (D1) to (D6), x is an integer of 1 to 3. y is an integer satisfying 0≦y≦5+2z−x. z is 0 or 1. g is an integer of 1 to 3. Each R ^C is independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Each R ^D is independently a hydrogen atom or a methyl group. R ¹⁰¹ , R ¹⁰² , R ¹⁰⁴ , and R ¹⁰⁵ are independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms. R ¹⁰³ , R ¹⁰⁶ , R ¹⁰⁷ and R ¹⁰⁸ are each independently a hydrogen atom, a hydrocarbyl group having 1 to 15 carbon atoms, a fluorinated hydrocarbyl group having 1 to 15 carbon atoms or an acid labile group, and when R ¹⁰³ , R ¹⁰⁶ , R ¹⁰⁷ and R ¹⁰⁸ are a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be present between the carbon-carbon bonds. R ¹⁰⁹ is a hydrogen atom or a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may be interposed by a group containing a hetero atom between the carbon-carbon bonds. R ¹¹⁰ is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may be interposed by a group containing a hetero atom between the carbon-carbon bonds. R ¹¹¹ is a saturated hydrocarbyl group having 1 to 20 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom, and a part of the -CH ₂ - of the saturated hydrocarbyl group may be substituted with an ester bond or an ether bond. Z ¹ is a (g+1)-valent hydrocarbon group having 1 to 20 carbon atoms or a (g+1)-valent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Z ² is a single bond, *-C(═O)-O-, or *-C(═O)-NH-. Z ³ is a single bond, -O-, *-C(═O)-O-Z ³¹ -Z ³² -, or *-C(═O)-NH-Z ³¹ -Z ³² -. Z ³¹ is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms. Z ³² is a single bond, an ester bond, an ether bond, or a sulfonamide bond. * indicates a bond to a carbon atom in the main chain.

In formulas (D1) and (D2), the saturated hydrocarbyl groups having 1 to 10 carbon atoms represented by R ¹⁰¹ , R ¹⁰² , R ¹⁰⁴ and R ¹⁰⁵ may be linear, branched or cyclic, and specific examples thereof include alkyl groups having 1 to 10 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl and n-decyl groups; and cyclic saturated hydrocarbyl groups having 3 to 10 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, adamantyl and norbornyl groups. Of these, saturated hydrocarbyl groups having 1 to 6 carbon atoms are preferred.

In formulas (D1) to (D4), the hydrocarbyl group having 1 to 15 carbon atoms represented by R ¹⁰³ , R ¹⁰⁶ , R ¹⁰⁷ and R ¹⁰⁸ may be any of linear, branched and cyclic, and specific examples thereof include an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 2 to 15 carbon atoms and an alkynyl group having 2 to 15 carbon atoms, with an alkyl group having 1 to 15 carbon atoms being preferred. Examples of the alkyl group include, in addition to those mentioned above, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group and an n-pentadecyl group. Furthermore, examples of the fluorinated hydrocarbyl group include groups in which some or all of the hydrogen atoms bonded to carbon atoms of the aforementioned hydrocarbyl groups have been substituted with fluorine atoms.

In formula (D4), examples of the (g+1)-valent hydrocarbon group having 1 to 20 carbon atoms represented by ^Z1 include a group in which g hydrogen atoms have been further removed from an alkyl group having 1 to 20 carbon atoms or a cyclic saturated hydrocarbyl group having 3 to 20 carbon atoms. Examples of the (g+1)-valent fluorinated hydrocarbon group having 1 to 20 carbon atoms represented by ^Z1 include groups in which at least one hydrogen atom of the above-mentioned (g+1)-valent hydrocarbon group has been substituted with a fluorine atom.

Specific examples of repeating units D1 to D4 include, but are not limited to, those shown below. In the following formula, R ^C is the same as defined above.

In formula (D5), examples of the hydrocarbyl group having 1 to 5 carbon atoms represented by R ¹⁰⁹ and R ¹¹⁰ include an alkyl group, an alkenyl group, an alkynyl group, etc., with an alkyl group being preferred. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, an n-pentyl group, etc. In addition, a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom may be present between the carbon-carbon bonds of the hydrocarbyl group.

In formula (D5), -OR ¹⁰⁹ is preferably a hydrophilic group. In this case, R ¹⁰⁹ is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms and an oxygen atom intervening between the carbon-carbon bonds, or the like.

In formula (D5), Z ² is preferably *-C(═O)-O- or *-C(═O)-NH-. Furthermore, R ^D is preferably a methyl group. The presence of a carbonyl group in ^{Z 2} improves the ability to trap acid derived from the antistatic film. Furthermore, when R ^D is a methyl group, a rigid polymer with a higher glass transition temperature (Tg) is obtained, thereby suppressing the diffusion of acid. This improves the stability of the resist film over time, and the resolution and pattern shape are not deteriorated.

Examples of the repeating unit D5 include, but are not limited to, those shown below: In the following formula, R ^D is the same as defined above.

In formula (D6), the saturated hydrocarbylene group having 1 to 10 carbon atoms represented by ^Z3 may be linear, branched, or cyclic, and specific examples thereof include a methanediyl group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a propane-2,2-diyl group, a butane-1,1-diyl group, a butane-1,2-diyl group, a butane-1,3-diyl group, a butane-2,3-diyl group, a butane-1,4-diyl group, and a 1,1-dimethylethane-1,2-diyl group.

In formula (D6), the saturated hydrocarbyl group having 1 to 20 carbon atoms and at least one hydrogen atom of which is substituted with a fluorine atom, represented by R ¹¹¹ , may be linear, branched, or cyclic, and specific examples thereof include an alkyl group having 1 to 20 carbon atoms or a cyclic saturated hydrocarbyl group having 3 to 20 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom.

Examples of the repeating unit D6 include, but are not limited to, those shown below: In the following formula, R ^D is the same as defined above.

The content of repeating units D1 to D4 is preferably 15 to 95 mol %, more preferably 20 to 85 mol %, of all repeating units of the fluorine atom-containing polymer. The content of repeating units D5 and/or D6 is preferably 5 to 85 mol %, more preferably 15 to 80 mol %, of all repeating units of the fluorine atom-containing polymer. Repeating units D1 to D6 may be used alone or in combination of two or more.

The fluorine atom-containing polymer may contain other repeating units in addition to the repeating units described above. Examples of such repeating units include those described in paragraphs [0046] to [0078] of JP 2014-177407 A. When the fluorine atom-containing polymer contains other repeating units, the content of such other repeating units is preferably 50 mol % or less of the total repeating units of the fluorine atom-containing polymer.

The fluorine atom-containing polymer can be synthesized by copolymerizing each monomer, which is protected with a protecting group as necessary, by a known method, and then carrying out a deprotection reaction as necessary. The copolymerization reaction is not particularly limited, but is preferably radical polymerization or anionic polymerization. For these methods, refer to JP-A-2004-115630.

The Mw of the fluorine atom-containing polymer is preferably 2000 to 50000, and more preferably 3000 to 20000. If the Mw is less than 2000, the diffusion of the acid is promoted, which may result in deterioration of the resolution and deterioration of the stability over time. If the Mw is too large, the solubility in the solvent may decrease, which may cause coating defects. In addition, the fluorine atom-containing polymer preferably has an Mw/Mn ratio of 1.0 to 2.2, and more preferably 1.0 to 1.7.

When the chemically amplified negative resist composition of the present invention contains (D) a fluorine atom-containing polymer, the content thereof is preferably 0.01 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, and even more preferably 0.5 to 10 parts by mass, relative to 80 parts by mass of (A) the base polymer. (D) The fluorine atom-containing polymer may be used alone or in combination of two or more kinds.

[(E) Quencher]
The chemically amplified negative resist composition of the present invention preferably contains a quencher as component (E). In the present invention, the quencher refers to a material that traps the acid generated from the photoacid generator in the chemically amplified resist composition, thereby preventing the acid from diffusing into unexposed areas and forming a desired pattern.

Examples of the quencher include conventional basic compounds. Examples of conventional basic compounds include primary, secondary, and tertiary aliphatic amines, mixed amines, aromatic amines, heterocyclic amines, nitrogen-containing compounds having a carboxy group, nitrogen-containing compounds having a sulfonyl group, nitrogen-containing compounds having a hydroxy group, nitrogen-containing compounds having a hydroxyphenyl group, alcoholic nitrogen-containing compounds, amides, imides, and carbamates. In particular, the primary, secondary, and tertiary amine compounds described in paragraphs [0146] to [0164] of JP 2008-111103 A, particularly amine compounds having a hydroxy group, an ether bond, an ester bond, a lactone ring, a cyano group, or a sulfonate ester bond, or compounds having a carbamate group described in JP Patent Publication No. 3790649 A are preferred. Preferred examples include tris[2-(methoxymethoxy)ethyl]amine, tris[2-(methoxymethoxy)ethyl]amine-N-oxide, dibutylaminobenzoic acid, morpholine derivatives, imidazole derivatives, etc. By adding such basic compounds, for example, it is possible to further suppress the diffusion rate of the acid in the resist film and correct the shape.

As another example of the quencher, there may be mentioned onium salts such as sulfonium salts, iodonium salts, and ammonium salts of carboxylic acids not fluorinated at the α-position, as described in JP-A-2008-158339. Sulfonic acids, imide acids, or methide acids fluorinated at the α-position are necessary for deprotecting acid labile groups, but carboxylic acids not fluorinated at the α-position are released by salt exchange with onium salts not fluorinated at the α-position. Carboxylic acids not fluorinated at the α-position hardly undergo a deprotection reaction, and therefore function as quenchers.

Examples of onium salts of carboxylic acids not fluorinated at the α-position include those represented by the following formula (E1).

In formula (E1), R ²⁰¹ is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a hydrogen atom or a heteroatom, except for those in which the hydrogen atom bonded to the carbon atom at the α-position of the carboxy group is substituted with a fluorine atom or a fluoroalkyl group.

The hydrocarbyl group represented by R ²⁰¹ may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 40 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, and tricyclo[5.2.1.0 ^2,6 ]Cyclic saturated hydrocarbyl groups having 3 to 40 carbon atoms, such as decyl group, adamantyl group, and adamantylmethyl group; alkenyl groups having 2 to 40 carbon atoms, such as vinyl group, allyl group, propenyl group, butenyl group, and hexenyl group; cyclic unsaturated aliphatic hydrocarbyl groups having 3 to 40 carbon atoms, such as cyclohexenyl group; phenyl group, naphthyl group, alkylphenyl group (2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 4-ethylphenyl group, 4-tert-butyl group, Examples of such aryl groups include aryl groups having 6 to 40 carbon atoms, such as di- or trialkylphenyl groups (2,4-dimethylphenyl group, 2,4,6-triisopropylphenyl group, etc.), alkylnaphthyl groups (methylnaphthyl group, ethylnaphthyl group, etc.), dialkylnaphthyl groups (dimethylnaphthyl group, diethylnaphthyl group, etc.); and aralkyl groups having 7 to 40 carbon atoms, such as benzyl group, 1-phenylethyl group, 2-phenylethyl group, etc.

In addition, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the _-CH2- of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a cyano group, a carbonyl group, an ether bond, a thioether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-O-C(=O)-), a haloalkyl group, etc. Examples of the hydrocarbyl group containing a heteroatom include heteroaryl groups such as a thienyl group; alkoxyphenyl groups such as a 4-hydroxyphenyl group, a 4-methoxyphenyl group, a 3-methoxyphenyl group, a 2-methoxyphenyl group, a 4-ethoxyphenyl group, a 4-tert-butoxyphenyl group, and a 3-tert-butoxyphenyl group; alkoxynaphthyl groups such as a methoxynaphthyl group, an ethoxynaphthyl group, an n-propoxynaphthyl group, and an n-butoxynaphthyl group; dialkoxynaphthyl groups such as a dimethoxynaphthyl group and a diethoxynaphthyl group; and aryloxoalkyl groups such as a 2-aryl-2-oxoethyl group, a 2-(1-naphthyl)-2-oxoethyl group, and a 2-(2-naphthyl)-2-oxoethyl group.

In formula (E1), Mq _A ⁺ is an onium cation. The onium cation is preferably a sulfonium cation, an iodonium cation, or an ammonium cation, and more preferably a sulfonium cation or an iodonium cation. Specific examples of the sulfonium cation include the same as those exemplified as the sulfonium cations of the repeating units A7 to A9. Specific examples of the iodonium cation include the same as those exemplified as the iodonium cations of the repeating units A11 to A13.

Examples of the anion of the onium salt represented by formula (E1) include, but are not limited to, those shown below.

As the quencher, a sulfonium salt of an iodized benzene ring-containing carboxylic acid represented by the following formula (E2) can also be suitably used.

In formula (E2), s is an integer from 1 to 5. t is an integer from 0 to 3, with the proviso that 1≦s+t≦5. u is an integer from 1 to 3.

In formula (E2), R ²¹¹ is a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an amino group, a nitro group, a cyano group, or a saturated hydrocarbyl group having 1 to 6 carbon atoms, in which some or all of the hydrogen atoms may be substituted with halogen atoms, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms, or a saturated hydrocarbylsulfonyloxy group having 1 to 4 carbon atoms, or -N(R ^211A )-C(═O)-R ^211B or -N(R ^211A )-C(═O)-O-R ^211B . R ^211A is a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms. R ^211B is a saturated hydrocarbyl group having 1 to 6 carbon atoms, or an unsaturated aliphatic hydrocarbyl group having 2 to 8 carbon atoms. When t and/or u is 2 or more, each R ²¹¹ may be the same or different.

In formula (E2), ^L1 is a single bond or a (u+1)-valent linking group having 1 to 20 carbon atoms, and may contain at least one selected from an ether bond, a carbonyl group, an ester bond, an amide bond, a sultone ring, a lactam ring, a carbonate bond, a halogen atom, a hydroxy group, and a carboxy group. The saturated hydrocarbyl group, saturated hydrocarbyloxy group, saturated hydrocarbylcarbonyloxy group, and saturated hydrocarbylsulfonyloxy group may be linear, branched, or cyclic.

In formula (E2), R ²¹² , R ²¹³ and R ²¹⁴ are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched or cyclic. Specific examples thereof include an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and an aralkyl group having 7 to 20 carbon atoms. In addition, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a hydroxy group, a carboxy group, a halogen atom, an oxo group, a cyano group, a nitro group, a sultone ring, a sulfo group or a sulfonium salt-containing group, and some of the -CH ₂ - of the hydrocarbyl group may be substituted with an ether bond, an ester bond, a carbonyl group, an amide bond, a carbonate bond or a sulfonate ester bond. In addition, R ²¹² and R ²¹³ may be bonded to each other to form a ring together with the sulfur atom to which they are bonded.

Specific examples of the compound represented by formula (E2) include those described in JP 2017-219836 A. The compound represented by formula (E2) has high absorption, a high sensitizing effect, and a high acid diffusion control effect.

As the quencher, a nitrogen atom-containing carboxylate compound represented by the following formula (E3) can also be used.

In formula (E3), R ²²¹ to R ²²⁴ are each independently a hydrogen atom, -L ² -CO ₂ ^- , or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. R ²²¹ and R ²²² , R ²²² and R ²²³ , or R ²²³ and R ²²⁴ may be bonded to each other to form a ring together with the carbon atom to which they are bonded. L ² is a single bond or a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. R ²²⁵ is a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom.

In formula (E3), ring ^Rr is a ring containing carbon atoms and nitrogen atoms and having 2 to 6 carbon atoms, some or all of the hydrogen atoms bonded to the carbon atoms of the ring may be substituted with a hydrocarbyl group having 1 to 20 carbon atoms or ^-L2 - _CO2- , and some of the carbon atoms of the ring may be substituted with a ^sulfur atom, an oxygen atom or a nitrogen atom. The ring may be an alicyclic ring or an aromatic ring and is preferably a 5- or 6-membered ring, specific examples of which include a pyridine ring, a pyrrole ring, a pyrrolidine ring, a piperidine ring, a pyrazole ring, an imidazoline ring, a pyridazine ring, a pyrimidine ring, a pyrazine ring, an imidazoline ring, an oxazole ring, a thiazole ring, a morpholine ring, a thiazine ring and a triazole ring.

The onium carboxylate represented by formula (E3) has at least one -L ² -CO ₂ ^- group, i.e., at least one of R ²²¹ to R ²²⁴ is -L ² -CO ₂ ^- , and/or at least one hydrogen atom bonded to a carbon atom of the R ring is substituted with -L ² -CO ₂ ^- .

In formula (E3), Mq _B ⁺ is a sulfonium cation, an iodonium cation or an ammonium cation, preferably a sulfonium cation. Specific examples of the sulfonium cation include the same as those exemplified as the sulfonium cations of the repeating units A7 to A9.

Examples of the anion of the compound represented by formula (E3) include, but are not limited to, those shown below.

Alternatively, a weak acid betaine type compound may be used as the quencher, specific examples of which include, but are not limited to, those shown below.

Further examples of the quencher include the polymer-type quencher described in JP 2008-239918 A. This enhances the rectangularity of the resist pattern by orienting on the surface of the resist film. Polymer-type quenchers also have the effect of preventing film loss in the pattern and rounding of the pattern top when a protective film for immersion exposure is applied.

When the chemically amplified negative resist composition of the present invention contains a quencher (E), the content thereof is preferably 0 to 50 parts by mass, more preferably 0.1 to 40 parts by mass, relative to 80 parts by mass of the base polymer (A). The quencher (E) may be used alone or in combination of two or more types.

When the chemically amplified negative resist composition of the present invention contains both the photoacid generator (B) and the quencher (E), the content ratio of the photoacid generator to the quencher ((B)/(E)) is preferably less than 6 by mass, more preferably less than 5, and even more preferably less than 4. If the content ratio of the photoacid generator to the quencher contained in the chemically amplified negative resist composition is within the above range, acid diffusion can be sufficiently suppressed, and excellent resolution and dimensional uniformity can be obtained.

[(F) Organic Solvent]
The chemically amplified negative resist composition of the present invention may contain an organic solvent as component (F). There is no particular limitation on the organic solvent as long as it is capable of dissolving each component. Examples of such organic solvents include ketones such as cyclohexanone, cyclopentanone, methyl-2-n-pentyl ketone, and 2-heptanone, as described in paragraphs [0144] to [0145] of JP-A-2008-111103; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and diacetone alcohol; propylene glycol monomethyl ether (PGME), ethylene glycol monomethyl ether, propylene glycol monoethyl ether, and ethylene glycol monoethyl ether. Examples of suitable solvents include ethers such as propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate, ethyl lactate (EL), ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, propylene glycol mono-tert-butyl ether acetate, and the like; lactones such as γ-butyrolactone, and mixed solvents thereof.

Among these organic solvents, 1-ethoxy-2-propanol, PGMEA, PGME, cyclohexanone, EL, γ-butyrolactone, and mixed solvents thereof are preferred.

When the chemically amplified negative resist composition of the present invention contains an organic solvent (F), the content thereof is preferably 200 to 10,000 parts by mass, and more preferably 400 to 6,000 parts by mass, per 80 parts by mass of the base polymer (B). The organic solvent (F) may be used alone or in combination of two or more kinds.

[(G) Surfactant]
The chemically amplified negative resist composition of the present invention may contain a commonly used surfactant in order to improve the coating property on the substrate. Examples of the surfactant include PF-636 (manufactured by OMNOVA SOLUTIONS) and FC-4430 (manufactured by 3M Corporation). In addition, as many examples are described in JP-A-2004-115630, many surfactants are known, and the surfactant can be selected by referring to these. When the chemically amplified negative resist composition of the present invention contains the surfactant (G), the content thereof is preferably 0 to 5 parts by mass relative to 80 parts by mass of the base polymer (B). The surfactant (G) may be used alone or in combination of two or more kinds.

[Method of forming a resist pattern]
The method for forming a resist pattern of the present invention includes the steps of forming a resist film on a substrate using the above-mentioned chemically amplified negative resist composition, irradiating the resist film with a pattern using high-energy rays (i.e., exposing the resist film with high-energy rays), and developing the resist film that has been irradiated with the pattern using an alkaline developer.

The substrate may be, for example, a substrate for manufacturing an integrated circuit (Si, SiO, SiO ₂ , SiN, SiON, TiN, WSi, BPSG, SOG, organic anti-reflective film, etc.), or a substrate for manufacturing a transmission or reflection type mask circuit (Cr, CrO, CrON, MoSi ₂ , Si, SiO, SiO ₂ , SiON, SiONC, CoTa, NiTa, TaBN, SnO ₂ , etc.). The chemically amplified negative resist composition is applied onto the substrate by a method such as spin coating to a film thickness of 0.03 to 2 μm, and the composition is prebaked on a hot plate, preferably at 60 to 150° C. for 1 to 20 minutes, more preferably at 80 to 140° C. for 1 to 10 minutes, to form a resist film.

Next, the resist film is exposed to high-energy radiation to irradiate a pattern. Examples of the high-energy radiation include ultraviolet radiation, far ultraviolet radiation, excimer laser light (KrF, ArF, etc.), EUV, X-rays, gamma rays, synchrotron radiation, and EB. In the present invention, it is preferable to use EUV or EB for exposure.

When ultraviolet light, far ultraviolet light, excimer laser light, EUV, X-rays, gamma rays or synchrotron radiation is used as the high energy radiation, a mask for forming a desired pattern is used and the exposure dose is preferably 1 to 500 mJ/cm ² , more preferably 10 to 400 mJ/cm ^2. When EB is used, direct exposure is performed to form a desired pattern, preferably at a dose of 1 to 500 μC/cm ² , more preferably 10 to 400 μC/cm ² .

In addition to the usual exposure method, in some cases, the immersion method can be used, in which the space between the mask and the resist film is immersed in liquid. In this case, a water-insoluble protective film can also be used.

Then, post-exposure bake (PEB) is performed on a hot plate, preferably at 60 to 150°C for 1 to 20 minutes, and more preferably at 80 to 140°C for 1 to 10 minutes.

Then, the substrate is developed using a developer of an alkaline aqueous solution such as 0.1 to 5% by weight, preferably 2 to 3% by weight, of TMAH or the like, preferably for 0.1 to 3 minutes, more preferably for 0.5 to 2 minutes, by a standard method such as the dip method, puddle method, or spray method, to form the desired pattern on the substrate.

The chemically amplified negative resist composition of the present invention is particularly useful for forming a pattern with good resolution and small LER. The chemically amplified negative resist composition of the present invention is particularly useful for forming a pattern on a substrate having a material on the surface that is prone to peeling or collapse of the pattern because it is difficult to obtain adhesion of the resist pattern. Examples of such substrates include a substrate having a sputtering film formed on the outermost surface of a chromium compound containing one or more light elements selected from metal chromium, oxygen, nitrogen, and carbon, and a substrate containing SiO, SiO _x , a tantalum compound, a molybdenum compound, a cobalt compound, a nickel compound, a tungsten compound, or a tin compound in the outermost layer. The chemically amplified negative resist composition of the present invention is particularly useful for forming a pattern using a photomask blank as the substrate. In this case, the photomask blank may be either a transmission type or a reflection type.

As a transmission type mask blank, a photomask blank having a light-shielding film made of a chromium-based material may be a photomask blank for a binary mask or a photomask blank for a phase shift mask. In the case of a photomask blank for a binary mask, the light-shielding film may have an anti-reflection layer and a light-shielding layer made of a chromium-based material, and the entire anti-reflection film on the surface side or only the surface side of the anti-reflection film on the surface side may be made of a chromium-based material, and the remaining part may be made of a silicon-based compound material that may contain, for example, a transition metal. In addition, in the case of a photomask blank for a phase shift mask, the target photomask blank may be a photomask blank for a phase shift mask having a chromium-based light-shielding film on a phase shift film.

The above-mentioned photomask blanks having a chromium-based material in the outermost layer are very well known, as exemplified in JP 2008-26500 A, JP 2007-302873 A, and the like as prior art therein, and detailed explanations are omitted here, but for example, when constructing a light-shielding film having an anti-reflection layer and a light-shielding layer using a chromium-based material, the following film configuration can be used.

When a light-shielding film having an anti-reflection layer and a light-shielding layer is formed from a chromium-based material, the layers may be laminated in the order of an anti-reflection layer and a light-shielding layer from the surface side, or an anti-reflection layer, a light-shielding layer and an anti-reflection layer. The anti-reflection layer and the light-shielding layer may each be multi-layered, and the composition between layers with different compositions may change discontinuously or may change continuously. The chromium-based material used is chromium metal or a material containing light elements such as oxygen, nitrogen and carbon in chromium metal. Specifically, chromium metal, chromium oxide, chromium nitride, chromium carbide, chromium oxide nitride, chromium carbide oxide, chromium nitride, chromium oxynitride, etc. can be used.

The reflective mask blank comprises a substrate, a multilayer reflective film formed on one main surface (front surface) of the substrate, specifically a multilayer reflective film that reflects exposure light such as EUV light, and an absorber film formed on the multilayer reflective film, specifically an absorber film that absorbs exposure light such as EUV light and reduces reflectance. From the reflective mask blank (EUV reflective mask blank), a reflective mask (EUV reflective mask) having an absorber pattern (absorber film pattern) formed by patterning the absorber film is manufactured. The wavelength of EUV light used in EUV lithography is 13 to 14 nm, and is usually light with a wavelength of about 13.5 nm.

The multilayer reflective film is usually preferably provided in contact with one main surface of the substrate, but it is also possible to provide an undercoat film between the substrate and the multilayer reflective film as long as the effect of the present invention is not lost. The absorber film may be formed in contact with the multilayer reflective film, but a protective film (protective film for the multilayer reflective film) may be provided between the multilayer reflective film and the absorber film, preferably in contact with the multilayer reflective film, more preferably in contact with the multilayer reflective film and the absorber film. The protective film is used to protect the multilayer reflective film during processing such as cleaning and correction. In addition, the protective film preferably has a function of protecting the multilayer reflective film when the absorber film is patterned by etching, and preventing the oxidation of the multilayer reflective film. On the other hand, a conductive film used for electrostatic chucking of the reflective mask to the exposure device may be provided under the other main surface (back surface) that is the surface opposite to the one main surface of the substrate, preferably in contact with the other main surface. In this case, one main surface of the substrate is the front surface and the upper side, and the other main surface is the back surface and the lower side, but the front and back and top and bottom of both are defined for convenience, and the one main surface and the other main surface are either of the two main surfaces (film formation surfaces) of the substrate, and the front and back and top and bottom are interchangeable. More specifically, it can be formed by a method such as that described in JP 2021-139970 A or exemplified as conventional technology therein.

According to the resist pattern forming method of the present invention, even when a substrate (e.g., a transmissive or reflective mask blank) is used whose outermost surface is made of a material that is likely to affect the resist pattern shape, such as a material containing chromium, silicon, or tantalum, it is possible to obtain a pattern that has extremely high resolution, small LER, excellent rectangularity, and excellent pattern fidelity.

The present invention will be specifically described below with reference to Synthesis Examples, Examples, and Comparative Examples, but the present invention is not limited to the following Examples. The apparatuses used are as follows.
IR: Thermo Fisher Scientific NICOLET 6700
・^1H -NMR: ECA-500 manufactured by JEOL Ltd.

（式中、Ｅｔは、エチル基である。） [1] Synthesis of Monomer [Example 1-1] Synthesis of Monomer A-1

(In the formula, Et is an ethyl group.)

(1) Synthesis of intermediate In-1 Under a nitrogen atmosphere, methyl magnesium chloride (3.0 M THF solution, 1200 mL) and THF (1200 mL) were charged into a reaction vessel, and the reaction vessel was heated until the temperature inside the reaction vessel reached 50° C. A solution of methyl 3-hydroxybenzoate (152.2 g) dissolved in THF (400 mL) was added dropwise while maintaining the temperature inside the reaction vessel at 60° C. or less. After the addition, the temperature inside the reaction vessel was increased to 60° C. and the reaction was aged for 3 hours. After aging, the reaction solution was cooled in an ice bath, and a solution consisting of ammonium chloride (360 g), 20% by mass hydrochloric acid (360 g), and water (1800 g) was added dropwise to terminate the reaction. Ethyl acetate (2000 mL) was added to the reaction solution to extract the target substance, which was then subjected to a typical aqueous work-up. The solvent was then distilled off, and hexane was added for recrystallization to obtain intermediate In-1 as white crystals (yield: 149.1 g, 98%).

(2) Synthesis of Monomer A-1 In a nitrogen atmosphere, intermediate In-1 (66.5 g) and triethylamine (66.3 g) were dissolved in THF (200 mL) in a reaction vessel. Then, methacrylic acid chloride (50.2 g) was added dropwise while maintaining the temperature in the reaction vessel at 30° C. or less. After the addition, the mixture was aged at room temperature for 2 hours. After aging, the reaction solution was cooled in an ice bath, and saturated sodium bicarbonate water (270 mL) was added dropwise to stop the reaction. Ethyl acetate (270 mL) was added to the reaction solution to extract the target product, which was then subjected to a normal aqueous work-up, the solvent was distilled off, and the product was purified by silica gel column chromatography to obtain Monomer A-1 as a colorless oil (yield 85.4 g, 89%).

The IR spectrum data and ¹ H-NMR results of Monomer A-1 are shown below.
IR(D-ATR): ν= 3435, 2976, 2929, 1734, 1637, 1609, 1587, 1485, 1433, 1402, 1378, 1365, 1323, 1297, 1256, 1187, 1166, 1131, 1002, 951, 912, 889, 834, 808, 785, 699, 642, 562, 478 cm ^-1 .
^1H -NMR(600MHz in DMSO-d6): δ= 7.33(2H, m), 7.22(1H, m), 6.98(1H, m), 6.26(1H, d), 5.88(1H, d), 5.09(1H, s), 2.00(3H, s), 1.41(6H, s) ppm.

Examples 1-2 to 1-9 Synthesis of Monomers A-2 to A-9 Using the corresponding raw materials, the following monomers A-2 to A-9 were synthesized.

Comparative Examples 1-1 to 1-7 Synthesis of Comparative Monomers AX-1 to AX-7 Comparative monomers AX-1 to AX-7 were synthesized as comparative monomers of unit A using corresponding raw materials.

[2] Polymer Synthesis Among the monomers used in the synthesis of the polymer, those other than the monomers A-1 to A-9 and the comparative monomers AX-1 to AX-7 are as follows.

[Example 2-1] Synthesis of polymer P-1 Under a nitrogen atmosphere, 24.8 g of 4-acetoxystyrene, 7.8 g of acenaphthylene, 67.4 g of 3-(1-hydroxy-1-methylethyl)phenyl 2-methyl-2-propionate, 9.8 g of dimethyl-2,2'-azobis(2-methylpropionate) (manufactured by Wako Pure Chemical Industries, Ltd., trade name V601), and 112 g of methyl ethyl ketone as a solvent were added to a 200 mL dropping cylinder to prepare solution A. Furthermore, 38 g of methyl ethyl ketone was added to another 500 mL polymerization flask under a nitrogen atmosphere, heated to 80°C, and while maintaining the temperature, solution A was dropped over 4 hours. After the dropwise addition, stirring was continued for 18 hours while maintaining the polymerization temperature at 80°C, and then cooled to room temperature. The obtained polymerization liquid was dropped into 1400 g of hexane, and the precipitated solid was filtered off. The filtered solid was washed twice with 280 g of hexane. The obtained solid was dissolved in 400 g of THF in a 1 L flask under a nitrogen atmosphere, and 29.4 g of ethanolamine was added and stirred at 60° C. for 3 hours. The reaction solution was concentrated under reduced pressure, and the obtained concentrate was dissolved in a mixed solvent of 300 g of ethyl acetate and 90 g of water. The obtained solution was transferred to a separatory funnel, and 29 g of acetic acid was added to perform a separation operation. The lower layer was distilled off, and 90 g of water and 39 g of pyridine were added to the obtained organic layer, and a separation operation was performed. The lower layer was distilled off, and 90 g of water was further added to the obtained organic layer, and water washing and separation were performed. Water washing and separation were performed a total of five times. The organic layer after separation was concentrated and then dissolved in 150 g of acetone. The acetone solution was dropped into 3000 g of water to obtain a crystallized precipitate, which was then filtered and washed with water. After suction filtration for 2 hours, the filtered product was dissolved in 150 g of acetone again. The acetone solution was dropped into 3000 g of water to obtain a crystallized precipitate, which was then filtered, washed with water, and dried to obtain 58.0 g of the target polymer P-1 as a white solid. When the polymer P-1 was measured by ¹³ C-NMR, ¹ H-NMR, and GPC, it was confirmed that it was the polymer shown below. The Mw is a polystyrene-equivalent value measured by GPC using DMF as a solvent.

[Examples 2-2 to 2-31, Comparative Examples 2-1 to 2-20] Synthesis of Polymers P-2 to P-31, CP-1 to CP-20 The polymers shown in Tables 1 to 3 below were synthesized in the same manner as in Example 2-1, except that the types and blending ratios of each monomer were changed.

[3] Preparation of chemically amplified negative resist composition [Examples 3-1 to 3-40, Comparative Examples 3-1 to 3-25]
Chemically amplified negative resist compositions (R-1 to R-40, CR-1 to CR-25) were prepared by dissolving each component in an organic solvent according to the composition shown in Tables 2 to 4 below, and filtering each of the resulting solutions through a UPE filter and/or a nylon filter selected from among filters with sizes of 10 nm, 5 nm, 3 nm, and 1 nm. Note that the organic solvent used was a mixed solvent of 790 parts by mass of PGMEA, 1580 parts by mass of EL, and 1580 parts by mass of PGME. In addition, fluorine atom-containing polymers (polymers FP-1 to FP-5) were added as additives, tetramethoxymethylglycoluril (TMGU) was added as a crosslinking agent, and PF-636 (manufactured by OMNOVA SOLUTIONS) was added as a surfactant to some of the compositions.

The structures of the photoacid generators PAG-A to PAG-E, the quenchers Q-1 to Q-5 and the fluorine atom-containing polymers FP-1 to FP-5 used in the resist compositions are as follows:

[2] EB Lithography Evaluation [Examples 3-1 to 3-40, Comparative Examples 3-1 to 3-25]
Each chemically amplified negative resist composition (R-1 to R-40, CR-1 to CR-25) was spin-coated onto a 152 mm square mask blank whose outermost surface was a silicon oxide film that had been treated with hexamethyldisilazane vapor prime using ACT-M (Tokyo Electron Ltd.), and pre-baked on a hot plate at 110°C for 600 seconds to produce a resist film with a thickness of 80 nm. The thickness of the resulting resist film was measured using an optical measuring device Nanospec (Nanometrics, Inc.). Measurements were performed at 81 points within the plane of the blank substrate, excluding the outer edge portion from the outer periphery to 10 mm inward, and the average film thickness and film thickness range were calculated.
The resist was exposed using an electron beam exposure device (EBM-5000plus, manufactured by NuFlare Technology, Inc., acceleration voltage 50 kV), subjected to PEB at 120° C. for 600 seconds, and developed with a 2.38% by mass aqueous TMAH solution to obtain a negative pattern.

The obtained resist pattern was evaluated as follows. The prepared patterned mask blank was observed with an overhead SEM (scanning electron microscope), and the exposure dose at which a 200 nm 1:1 line and space (LS) pattern was resolved at 1:1 was defined as the optimum exposure dose (μC/cm ² ), and the minimum dimension at the exposure dose at which a 200 nm LS pattern was resolved at 1:1 was defined as the resolution (limit resolution). For the 200 nm LS pattern obtained by irradiation with the optimum exposure dose, 80 edge detection was performed for each of the 32 edges of the 200 nm LS pattern using an SEM, and the triple value (3σ) of the variation (standard deviation, σ) was obtained, which was defined as the LER. The pattern shape was visually judged to be rectangular or not. For the pattern fidelity evaluation, the Area Loss value (%) of one corner of the dot pattern was calculated when a square dot pattern of 120 nm size was arranged at a density of 36%, and it can be determined that the smaller the value, the better the rectangularity of the dot shape. The results are shown in Tables 7 and 8.

As described above, by using the chemically amplified negative resist composition of the present invention, a pattern with extremely high resolution and excellent LER, shape, and pattern fidelity can be formed. The method for forming a resist pattern using the chemically amplified negative resist composition of the present invention is useful for semiconductor device manufacturing, particularly photolithography in the processing of transmissive or reflective mask blanks.

Claims (20)

A monomer represented by the following formula (A1):

(In the formula, a is an integer of 0 to 4.
R ^A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.
L ^A is —O— or —NH—.
L ^B is a single bond, an ether bond, an ester bond or an amide bond.
X ^L is a single bond or a hydrocarbylene group having 1 to 40 carbon atoms which may contain a heteroatom.
R ¹ is a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom.
R ² and R ³ are each independently a hydrogen atom, a saturated hydrocarbyl group having 1 to 15 carbon atoms, or an aryl group having 6 to 15 carbon atoms, the hydrocarbyl group may be substituted with a hydroxy group or a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, and the aryl group may have a substituent. However, R ² and R ³ cannot be hydrogen atoms at the same time. R ² and R ³ may be bonded to each other to form a ring together with the carbon atom to which they are bonded, and a portion of -CH ₂ - of the ring may be substituted with -O- or -S-.
^W1 is a hydrogen atom, an aliphatic hydrocarbyl group having 1 to 10 carbon atoms, an aliphatic hydrocarbylcarbonyl group having 2 to 10 carbon atoms, or an aryl group having 6 to 15 carbon atoms, and the aryl group may have a substituent. The monomer according to claim 1, represented by the following formula (A1-1):

(In the formula, a, R ^A , L ^A , R ¹ , R ² , R ³ and W ¹ are the same as defined above.) The monomer according to claim 2, represented by the following formula (A1-2):

(In the formula, a, R ^A , L ^A , R ¹ , R ² and R ³ are the same as defined above.) A polymer containing repeating units derived from the monomer of claim 1. The polymer according to claim 4, further comprising a repeating unit represented by the following formula (A2):

(In the formula, b1 is 0 or 1. b2 is an integer from 0 to 2. b3 is an integer that satisfies 0≦b3≦5+2(b2)−b4. b4 is an integer from 1 to 3.
R ^A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.
R ¹¹ is a halogen atom, a saturated hydrocarbyl group having 1 to 6 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom.
A ¹ is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and a part of the —CH ₂ — in the saturated hydrocarbylene group may be substituted with —O—. The polymer according to claim 4, further comprising at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (A3), a repeating unit represented by the following formula (A4), and a repeating unit represented by the following formula (A5):

(In the formula, c and d are each independently an integer of 0 to 4. e1 is 0 or 1. e2 is an integer of 0 to 2. e3 is an integer of 0 to 5.
R ^A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.
R ²¹ and R ²² each independently represent a hydroxy group, a halogen atom, a saturated hydrocarbyl group having 1 to 8 carbon atoms which may be substituted with a halogen atom, a saturated hydrocarbyloxy group having 1 to 8 carbon atoms which may be substituted with a halogen atom, or a saturated hydrocarbylcarbonyloxy group having 2 to 8 carbon atoms which may be substituted with a halogen atom.
R ²³ is a saturated hydrocarbyl group having 1 to 20 carbon atoms, a saturated hydrocarbyloxy group having 1 to 20 carbon atoms, a saturated hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms, a saturated hydrocarbyloxyhydrocarbyl group having 2 to 20 carbon atoms, a saturated hydrocarbylthiohydrocarbyl group having 2 to 20 carbon atoms, a halogen atom, a nitro group, a cyano group, a saturated hydrocarbylsulfinyl group having 1 to 20 carbon atoms, or a saturated hydrocarbylsulfonyl group having 1 to 20 carbon atoms.
^A2 is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms, and a part of the _--CH2-- of the saturated hydrocarbylene group may be substituted with --O--. The polymer according to claim 4, further comprising at least one repeating unit selected from the repeating units represented by the following formulas (A6) to (A13):

(In the formula, each R ^B independently represents a hydrogen atom or a methyl group.
X ¹ 's are each independently a single bond, an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, -O-X ¹¹ -, -C(═O)-O-X ¹¹ -, or -C(═O)-NH-X ¹¹ -, and X ¹¹ is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a naphthylene group, or a group having 7 to 18 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond, or a hydroxy group.
Each X ² is independently a single bond or —X ²¹ —C(═O)—O—, and X ²¹ is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom.
Each ^X3 is independently a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, -O- ^X31- , -C(=O)-O- ^X31- or -C(=O)-NH- ^X31- , and ^X31 is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group or a group having 7 to 20 carbon atoms obtained by combining these, and may contain a carbonyl group, an ester bond, an ether bond or a hydroxy group.
Each X ⁴ is independently a single bond or a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom.
f1 and f2 each independently represent 0 or 1, provided that when X ⁴ is a single bond, f1 and f2 are 0.
R ³¹ to R ⁴⁸ are each independently a halogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. R ³¹ and R ³² may be bonded to each other to form a ring together with the sulfur atom to which they are bonded, and R ³³ and R ³⁴ , R ³⁶ and R ³⁷ , or R ³⁹ and R ⁴⁰ may be bonded to each other to form a ring together with the sulfur atom to which they are bonded.
R ^HF is a hydrogen atom or a trifluoromethyl group.
^Xa- is a non-nucleophilic counter ion. A chemically amplified negative resist composition comprising a base polymer containing the polymer according to any one of claims 4 to 7. The chemically amplified negative resist composition according to claim 8, wherein the content of repeating units having an aromatic ring skeleton among all repeating units of the polymer contained in the base polymer is 60 mol % or more. The chemically amplified negative resist composition according to claim 8, further comprising (B) an acid generator. The chemically amplified negative resist composition according to claim 8, further comprising (C) a crosslinking agent. The chemically amplified negative resist composition according to claim 8, which does not contain a crosslinking agent. The chemically amplified negative resist composition according to claim 8, further comprising (D) a fluorine atom-containing polymer which contains at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (D1), a repeating unit represented by the following formula (D2), a repeating unit represented by the following formula (D3), and a repeating unit represented by the following formula (D4), and which may further contain at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (D5) and a repeating unit represented by the following formula (D6):

(In the formula, x is an integer of 1 to 3. y is an integer satisfying 0≦y≦5+2z−x. z is 0 or 1. g is an integer of 1 to 3.
Each R ^C independently represents a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.
Each R ^D independently represents a hydrogen atom or a methyl group.
R ¹⁰¹ , R ¹⁰² , R ¹⁰⁴ and R ¹⁰⁵ each independently represent a hydrogen atom or a saturated hydrocarbyl group having 1 to 10 carbon atoms.
R ¹⁰³ , R ¹⁰⁶ , R ¹⁰⁷ and R ¹⁰⁸ each independently represent a hydrogen atom, a hydrocarbyl group having 1 to 15 carbon atoms, a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, or an acid labile group, and when R ¹⁰³ , R ¹⁰⁶ , R ¹⁰⁷ and R ¹⁰⁸ are a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be present between the carbon-carbon bonds.
R ¹⁰⁹ is a hydrogen atom or a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a heteroatom-containing group interposed between its carbon-carbon bonds.
R ¹¹⁰ is a linear or branched hydrocarbyl group having 1 to 5 carbon atoms which may have a heteroatom-containing group interposed between its carbon-carbon bonds.
R ¹¹¹ is a saturated hydrocarbyl group having 1 to 20 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom, and a portion of the --CH ₂ -- in the saturated hydrocarbyl group may be substituted with an ester bond or an ether bond.
Z ¹ is a (g+1)-valent hydrocarbon group having 1 to 20 carbon atoms or a (g+1)-valent fluorinated hydrocarbon group having 1 to 20 carbon atoms.
^Z2 is a single bond, *-C(=O)-O-, or *-C(=O)-NH-.
Z ³ is a single bond, --O--, *-C(=O)--O--Z ³¹ -Z ³² - or *-C(=O)--NH--Z ³¹ -Z ³² -. Z ³¹ is a single bond or a saturated hydrocarbylene group having 1 to 10 carbon atoms. Z ³² is a single bond, an ester bond, an ether bond or a sulfonamide bond.
* indicates a bond to a carbon atom in the main chain.) The negative resist composition according to claim 8, further comprising (E) a quencher. The chemically amplified negative resist composition according to claim 8, further comprising (F) an organic solvent. A method for forming a resist pattern comprising the steps of forming a resist film on a substrate using the chemically amplified negative resist composition according to claim 8, irradiating the resist film with a pattern using high-energy radiation, and developing the resist film irradiated with the pattern using an alkaline developer. The method for forming a resist pattern according to claim 16, wherein the high-energy radiation is extreme ultraviolet radiation or an electron beam. The method for forming a resist pattern according to claim 16, wherein the outermost surface of the substrate is made of a material containing at least one selected from the group consisting of chromium, silicon, tantalum, molybdenum, cobalt, nickel, tungsten, and tin. The method for forming a resist pattern according to claim 16, wherein the substrate is a transmission type or a reflection type mask blank. A transmission or reflection mask blank coated with the chemically amplified negative resist composition according to claim 8.